A step-parent over the age of eighteen who is presently married to the consenting natural or adoptive parent of a child can under California law become the legal adoptive parent of the child provided one of several circumstances exists. If the facts required by law exist, the step-parent can petition to adopt the child. The adoption by a step-parent, like any other adoption, results in severing the absent biological parent's legal connection to the child, ending that person's rights (including custodial and visitation rights) and responsibilities (including financial support).

There are four possible routes to a successful step-parent adoption.

If the absent parent decides to contest the termination of rights and the adoption, the legal proceedings can become somewhat costly, depending on what the legal issues are and how complicated it may be to prove the necessary facts.

If the Department of Social Services investigates and then for some reason recommends against the adoption (a rare occurrence in a step-parent adoption), the Court will normally follow the recommendation. It is possible, however, to challenge the negative recommendation and attempt to persuade the Court to approve the adoption; it is also possible to appeal a negative ruling. These situations are very rare, and quite expensive.

Normally, step-parent adoptions are not extremely costly. It is even possible to do the legal work without a lawyer, although most people prefer to have a lawyer handle the court proceedings for them. Most lawyers charge an hourly rate and can give an approximate estimate of the cost of an uncontested step-parent adoption.