Here’s a deep-dive, practice-oriented legal article—Philippine context—on Legal Remedies for Infidelity by a Partner. It spans criminal, civil, and family-law routes; how to gather evidence legally; what outcomes to expect; and ready-to-use pleading skeletons.

1) First principles (what “infidelity” means in law)

“Infidelity” isn’t a single cause of action. Depending on facts, it can trigger several distinct remedies:

Criminal: Adultery or Concubinage under the Revised Penal Code (RPC), and VAWC (psychological violence) under R.A. 9262.
Family law: Legal Separation, Declaration of Nullity (void marriage), or Annulment (voidable marriage), Custody, Support, Dissolution of property regime.
Civil/Tort: Damages against the unfaithful spouse/partner (and, in proper cases, against the paramour) for acts contrary to law, morals, good customs (Civil Code Arts. 19, 20, 21), privacy violations, or humiliation.
Protective: Protection Orders (BPO/TPO/PPO) under R.A. 9262.

Strategy rule: Pick the track(s) that match your goal—safety, accountability, financial security, status (marriage), or quiet exit. These can be combined (e.g., VAWC + Legal Separation; or Civil Damages + Nullity).

2) Criminal remedies

2.1 Adultery (RPC)

Who: A married woman who has sexual intercourse with a man not her husband, and the man who knows she is married.
Key elements: (a) Valid marriage; (b) Sexual intercourse; (c) Knowledge of marriage by the other party.
Filing rule (private crime): Only the husband can file, and he must include both the wife and the alleged paramour if both are alive. Consent or pardon bars the case (and must cover both).

2.2 Concubinage (RPC)

Who: A married man who (any of the following): keeps a mistress in the conjugal dwelling; or has sexual intercourse under scandalous circumstances; or cohabits with her in another place. The woman may be liable (usually destierro).
Filing rule: Only the wife can file, and she must include both husband and concubine if both are alive. Consent/pardon likewise bars.

Practical note: Adultery is easier to prove (single act of sexual intercourse). Concubinage usually needs specific modes (conjugal dwelling, scandal, or cohabitation), not just a one-off tryst.

2.3 VAWC (R.A. 9262) — psychological violence

Who: Crimes committed by a husband or intimate partner against a woman (and/or her child), including acts causing psychological/emotional distress.
When tied to infidelity: Repeated marital infidelity, public humiliation, financial abandonment, or threats can amount to psychological violence if they cause mental/emotional anguish.
Reliefs: Criminal penalties, plus Protection Orders (see §5), custody, support, exclusive use of residence, and restitution as ancillary civil reliefs in the criminal case.
Venue: Often at the victim’s residence for accessibility.

3) Family-law remedies

3.1 Legal Separation

Ground: Marital infidelity qualifies (also sexual infidelity, per se).
Effect:
- Spouses live separately;
- Property regime (absolute community/conjugal partnership) is dissolved and liquidated;
- Forfeiture: the guilty spouse’s share in the net profits may be forfeited in favor of common children (and, in their default, the innocent spouse);
- Custody: usually to the innocent spouse, subject to the best-interest of the child;
- Inheritance: the guilty spouse may be disqualified from inheriting intestate from the innocent spouse.
- No remarriage: Marriage bond subsists; you cannot remarry.

3.2 Declaration of Nullity / Annulment

Infidelity is not itself a ground. But your fact pattern may align with a void or voidable marriage:
- Void (e.g., psychological incapacity; bigamy; lack of essential/formal requisites).
- Voidable (e.g., fraud, insanity at marriage, etc.).
Effect: Marriage tie severed (once final); you can remarry. Property and child effects depend on the specific ground and good faith.

3.3 Recognition of Foreign Divorce (Art. 26(2))

If the foreign spouse validly obtains a divorce abroad, the Filipino spouse can seek recognition in Philippine courts (to remarry and settle status/property). (Special rules apply depending on citizenship at time of divorce.)

3.4 Custody and Support

Custody: Best interests of the child control. Infidelity alone doesn’t automatically disqualify a parent, but abuse/VAWC and moral unfitness weigh heavily.
Support: Spousal and child support may be provisionally ordered while the case is pending; final support is fixed at judgment.

4) Civil/Tort damages

You can sue the unfaithful spouse and, in proper cases, the paramour, for moral, exemplary, and actual damages under Civil Code Arts. 19, 20, 21 (abuse of rights/acts contra bonos mores), especially where the affair involved public scandal, humiliation, harassment, or intrusion into family privacy.

Alienation of affections as a U.S.-style tort is not a standalone Philippine cause of action; frame the case under Articles 19/20/21 and privacy principles.
You may consolidate damage claims with family/criminal actions or file separately.

5) Protection Orders (R.A. 9262)

If infidelity is intertwined with abuse (threats, harassment, stalking, economic abuse, psychological violence), seek:

Barangay Protection Order (BPO) — quick, limited scope;
Temporary Protection Order (TPO) — ex parte, short-term;
Permanent Protection Order (PPO) — after hearing.

Reliefs may include: stay-away orders, exclusive use of home, custody/visitation rules, support, firearms surrender, and law-enforcement assistance.

6) Evidence: what works—and what’s illegal

6.1 Admissible & practical

Direct proof of sexual relations (rare).
Circumstantial: consistent patterns—hotel check-ins, travel records, affectionate public posts, cohabitation evidence, shared leases, birth records, admissions, text/app messages, emails, photos—authenticated as electronic evidence (follow the Rules on Electronic Evidence: show authorship, integrity, and origin; keep original devices/metadata where possible).
Financial: remittances, gifts, joint purchases.
Witness: neighbors, staff, security, admissions to friends.

6.2 Do not break the law to get proof

Anti-Wiretapping Act (R.A. 4200): No secret audio recording of private communications without consent.
Anti-Photo/Video Voyeurism (R.A. 9995): No non-consensual intimate imaging or sharing.
Data Privacy Act (R.A. 10173): Handle personal data lawfully; no doxxing.
Cybercrime Act (R.A. 10175): Beware cyber libel—don’t post accusations online.

Bottom line: Gather evidence lawfully; authenticity beats volume. When in doubt, consult counsel before collecting or sharing.

7) Choosing your remedy: quick matrix

Goal	Fastest tool	Upside	Tradeoffs
Safety / stop harassment	BPO/TPO/PPO (VAWC)	Immediate, practical relief	Needs abuse/violence angle
Criminal accountability	Adultery/Concubinage or VAWC	Deterrence; moral vindication	Private complaint rules; heavier proof
Separate lives + divide property	Legal Separation	Dissolves property regime; custody/support orders	Can’t remarry
End marriage to remarry	Nullity/Annulment (or foreign divorce recognition)	Status reset; finality	Not based on infidelity itself; evidentiary burden
Financial compensation	Civil damages	Moral/exemplary/actual damages	Proof of wrongful acts + causation

8) Outcomes you can expect

Criminal: Possible conviction; civil liability can be adjudged in the criminal case.
VAWC: Protection orders; penalties; custody and support as ancillary reliefs.
Legal Separation: Property regime dissolved; forfeiture of guilty spouse’s share in net profits to common children; custody orders; no remarriage.
Nullity/Annulment: Marriage tie severed (once final); property/liquidation per ground; children’s status unaffected (legitimacy follows the law).
Civil: Moral/exemplary/actual damages + attorney’s fees when warranted.

9) Filing paths & venue (nutshell)

Adultery/Concubinage: Affidavit-Complaint before the Prosecutor’s Office in the place of commission. Must be filed by the offended spouse, against both if living.
VAWC: Police/Prosecutor; Protection Orders at Barangay (BPO) or Family/RTC (TPO/PPO).
Legal Separation / Nullity / Annulment / Recognition of Foreign Divorce: Family Court where either party resides; governed by special rules (verified petition, service, mandatory conferences, possible social worker’s report).
Civil Damages: RTC (or first-level court depending on amount); venue typically where plaintiff resides or where cause of action arose.

10) Smart sequencing (common playbooks)

If abuse is present: File VAWC → get TPO/PPO (safety, support, custody) → then choose Legal Separation or Nullity.
If you want status change quickly (and facts fit): Assess Nullity/Annulment first; consider civil damages in parallel or later.
If you want deterrence: Adultery/Concubinage (respect filing rules) + optional civil damages.
Quiet exit: Consider SEnA/mediation for support/property; then family-court petition.

11) Evidence checklist (print-friendly)

☐ Marriage certificate; children’s birth certificates
☐ Proof of infidelity: hotel/booking, messages, emails, photos (lawfully obtained), admissions
☐ Proof of cohabitation: leases, barangay certificates, deliveries, utilities
☐ Proof of psychological distress: medical/psych notes, testimony, work impact
☐ Financials: remittances, gifts, transfers
☐ Witness details: names/contact; short sworn statements
☐ Any threats/harassment: screenshots, call logs
☐ Keep originals; export metadata-intact copies; avoid illegal recordings

12) Pleading skeletons you can adapt

12.1 Affidavit-Complaint (Adultery/Concubinage)

I, [Name], Filipino, married to [Spouse], state:

1) We were validly married on [date], as shown by [Annex A].
2) On [dates], at [place], Respondents [Spouse] and [Paramour] [acts: sexual intercourse/cohabitation/kept in conjugal dwelling/scandalous circumstances], as shown by [Annexes].
3) I did not consent to or pardon these acts. I file this complaint against both respondents, who are alive and can be served.
PRAYER: File the appropriate Information(s) and prosecute.

[Signature; ID details; Jurat]

12.2 Petition for Legal Separation — Outline

CAPTION (Family Court)

Verified Petition for Legal Separation

- Parties, marriage details, children, property regime
- Grounds: Marital infidelity (facts, dates, supporting proof)
- Reliefs: Decree of legal separation; dissolution & liquidation of property regime;
  forfeiture of guilty spouse’s share in net profits in favor of common children;
  custody & visitation orders; support; exclusive use of family home; protective reliefs
- Verification & Certificate against Forum Shopping

12.3 Petition for Declaration of Nullity/Annulment — Outline

- Ground (e.g., psychological incapacity/bigamy/fraud): factual specifics
- Prayer: Nullity/Annulment; effects on property; custody; support; use of surname; annotations

12.4 Civil Complaint for Damages (Arts. 19/20/21)

- Defendant(s): Unfaithful spouse and/or paramour
- Wrongful acts: persistent affair, public humiliation, intrusion into family privacy
- Injury: mental anguish, wounded feelings, reputational harm, expenses
- Reliefs: Moral, exemplary, actual damages; attorney’s fees; injunctions (if needed)

12.5 VAWC Petition for Protection Order (TPO/PPO)

- Parties & relationship
- Acts of psychological violence tied to infidelity (facts, patterns, effects)
- Urgent reliefs: stay-away; custody; support; exclusive home use; firearm surrender; law-enforcement assistance
- Attach evidence; ex parte prayer for TPO

13) Practical tips (win the case, protect yourself)

Keep calm, go lawful: Never entrap with illegal recordings.
Document now: Write a dated timeline; preserve chats/emails in exported form; keep devices safe.
Pick the right forum: Don’t file adultery/concubinage without meeting private-complaint rules.
Mind collateral crimes: Avoid social-media rants (risk of cyber libel).
Think finances early: Ask for support pendente lite, access to family home, and safeguards over bank accounts and conjugal/ACP assets.
Children first: Stability of schooling, caregiving, and routines helps custody.
Settlement? You can settle civil/family issues (support, property, parenting plan). Criminal cases have limits on compromise, and public crimes generally cannot be the subject of pardon except as the law allows (note private-crime pardon/consent rules).

14) FAQs (quick answers)

Can I sue the third party? Yes, for damages under Arts. 19/20/21 if their acts caused you actionable harm; criminal liability attaches only in adultery/concubinage with the spouse.
Is a one-night stand enough? For adultery, one act can suffice (if proven). For concubinage, the law often expects cohabitation, conjugal dwelling, or scandalous sexual conduct—not a single secret encounter.
Will infidelity automatically lose custody? Not by itself. The court looks at best interests of the child; abuse and neglect matter far more.
Can I remarry after legal separation? No. Only nullity/annulment (or recognized foreign divorce / Muslim divorce under special law) changes civil status to permit remarriage.

15) Action plan (48-hour checklist)

Safety first: If there’s harassment or threats, seek a TPO/BPO immediately.
Preserve evidence: Export chats/emails (with headers/metadata), keep originals, list witnesses.
Decide your goal: Protection? Status change? Money/property? Accountability?
Pick the track(s): VAWC; Adultery/Concubinage; Legal Separation; Nullity/Annulment; Civil Damages.
File smart: Use the pleading skeletons; request support pendente lite, custody, exclusive use as needed.
Don’t burn bridges you’ll need: Avoid illegal proofs or online defamation; let the paper and facts work.

If you want, tell me your facts and goals (kids, assets, safety concerns), and I’ll draft a tailored roadmap (which cases to file first, venue, pleadings to prepare this week, and a lawful evidence plan).