Adult Adoption in Washington: Consent, Process, and Effects

Adult adoption in Washington is a Superior Court process in which one adult legally becomes the parent of another, accomplished by a joint petition signed by both people under penalty of perjury, with the adoptee’s written consent attached. Once the judge signs the decree, the adoptee is treated as the adoptive parent’s child for every legal purpose that family relationship touches: inheritance, medical decision-making priority, and a new birth certificate in the adoptive parent’s name.¹²

The statute is unusually short for a family law matter. No home study, no background check, no biological parent consent. The adoption turns almost entirely on whether the two adults involved both want it and whether the court sees any reason to question that.

Who Can Adopt and Who Must Consent

Anyone eighteen or older can be adopted. The only required signatures on the petition are the person adopting and the person being adopted, and the adoptee also files a separate written consent. The statute states plainly that no other consents are required, meaning biological parents, former adoptive parents, and other relatives cannot block the adoption or weigh in on it.¹

Residency matters, but only lightly. The adoptee does not need to live in Washington. At least one party, the petitioner or the adoptee, must be domiciled or actually residing in the state when the petition is filed.³ The petition is filed in the Superior Court of the county where the petitioner lives or where the adoptee is domiciled.⁴

If the person adopting is married, their spouse has to join in the petition by co-signing. The court cannot waive this.⁴ A married petitioner whose spouse objects cannot move forward. The adoptee’s spouse, if any, does not have to join or consent.

Both people also need legal capacity to understand what they are doing. The decree is permanent, it rewrites inheritance rights, and it severs legal ties to the adoptee’s biological parents. Someone under a guardianship that limits legal decision-making may need to resolve that side of things first.

Filing the Petition

Washington does not publish statewide standard forms for adoption petitions, and many county Superior Court Clerk’s offices do not stock packets.⁵ Most petitioners hire an attorney to draft the paperwork, though it can be done without one.

The petition needs to include:

The petitioner’s name and address
The adoptee’s name, gender, and place and date of birth, if known
A statement about whether the Indian Child Welfare Act applies
The name and address of any person or agency with custody of the adoptee

Both the person adopting and the adoptee sign the petition. If the petitioner is married, so does the spouse. The adoptee’s separate written consent is filed with it.⁴¹ The statute calls for signatures under penalty of perjury, which is not the same as notarization; some attorneys notarize the consent as a precaution, but the law does not require it.

Bring government-issued identification and a certified copy of the adoptee’s birth certificate. The birth certificate establishes the baseline record that will be replaced after finalization. If the adoptee wants a new surname, request the name change in the petition itself so the judge can include it in the decree.

The Court Hearing

After the clerk processes the filing, the court schedules a hearing. The judge has to be satisfied of two things before signing the decree: that all required consents are valid, and that the adoption is in the best interest of the adoptee.⁶ When both adults clearly want the adoption, the best-interest question is usually quick. Judges watch for signs of coercion, fraud, or an attempt to use adoption to work around some other area of law.

The hearing is short. Both people appear, confirm their identities, and affirm the adoption is voluntary. The judge may ask about the relationship and why they are pursuing it, then signs the decree. Denials in uncontested adult adoptions are rare but possible if the judge suspects an improper purpose.

What the Decree Changes

Once signed, the decree makes the adoptee, in the statute’s language, “to all intents and purposes, and for all legal incidents, the child, legal heir, and lawful issue of the adoptive parent.”² A few effects matter most in day-to-day life.

Ties to Biological Parents Are Cut

The decree strips legal rights and obligations from any parent who did not join the petition and is not married to the adoptive parent. The adoptee no longer owes any legal duty of obedience or support to those biological parents.² The severance is complete and permanent, with the narrow exception of past-due child support, which survives. In a stepparent-style adult adoption where the biological parent is married to the adopting person, that biological parent’s rights remain intact.

Inheritance Shifts

Washington treats an adopted person identically to a biological child for inheritance. The adoptee can inherit from the adoptive parent through intestate succession when there is no will. The counterpart is just as real: a lawfully adopted person is no longer an heir of their biological parents for probate purposes.⁷ Think through that trade before filing.

A New Birth Certificate

After the decree, the parties can submit a certified copy to the state registrar of vital statistics, who issues a new birth certificate naming the adoptive parent. If the adoptee was born in Washington, the Department of Health issues it; if born in another state or U.S. territory, the registrar forwards the adoption certificate to the correct agency in the birth state.⁸ The new certificate makes no mention of the adoption and reflects any court-ordered name change. It becomes the basis for updating Social Security records and state identification.

Medical Decision-Making

When a Washington patient cannot make healthcare decisions and has no advance directive or power of attorney, state law sets a priority list of surrogate decision-makers. Parents rank fifth, after a guardian, an attorney-in-fact, a spouse or domestic partner, and the patient’s adult children.⁹ Without the adoption, someone acting as a parent figure has no standing on that list. The decree puts them on it. An adopted adult child also gains standing to make decisions for the adoptive parent, ranking just below a spouse or domestic partner.

What Adult Adoption Will Not Do

Two common motivations do not survive contact with the actual law.

Immigration status is one. Federal immigration law defines a “child” for immigration purposes with a strict age threshold: the adoption generally must have occurred before the child turned sixteen.¹⁰ An adult adoptee does not qualify, and the adoption cannot anchor a family-based petition. The Child Citizenship Act of 2000 also requires that its criteria be met before age eighteen.¹¹

Social Security survivor benefits are the other. The Social Security Administration generally limits child’s benefits to unmarried children under eighteen, under nineteen and still in secondary school, or eighteen and older with a disability that began before age twenty-two. An adult adoptee without a qualifying disability will not draw survivor benefits on the adoptive parent’s record, regardless of the decree.

What It Costs

The main out-of-pocket cost is the court filing fee, which varies by county. King County charges $310 to file an adoption.¹² Attorney fees for an uncontested adult adoption typically run between $2,000 and $3,500, depending on the lawyer and the complexity of the paperwork. Expect a small administrative fee of roughly $15 to $20 for the new birth certificate after the decree.

Fee waivers may be available for petitioners who meet the court’s income thresholds. Ask the clerk’s office about a fee waiver application before you file if the filing fee is a hardship.

1
Washington State Legislature. Washington Code 26.33.030 – Adoption of an Adult
2
Washington State Legislature. Washington Code 26.33.260 – Decree of Adoption Legal Effect
3
Social Security Administration. PR 01310.053 – Washington
4
Washington State Legislature. Washington Code 26.33.150 – Petition for Adoption Filing Contents Preplacement Report Required
5
Whatcom County. Adoption
6
Washington State Legislature. Washington Code 26.33.240 – Petition for Adoption Hearing Decree
7
Washington State Legislature. Washington Code 11.04.085 – Inheritance by Adopted Child
8
Washington State Legislature. Washington Code 70.58A – Vital Statistics
9
Washington State Legislature. Washington Code 7.70.065 – Informed Consent for Health Care Surrogate Decision Maker
10
U.S. Citizenship and Immigration Services. Volume 5 Part F Chapter 2 – Definitions
11
U.S. Citizenship and Immigration Services. Adult Adoptees and U.S. Citizenship
12
King County. Superior Court Clerks Office Fee and Payment Information