A legal proceeding that involves issues of visitation, custody and child support in unmarried parents is known as a Paternity lawsuit. It is similar to a dissolution proceeding and involves the establishment of parentage.

Establishing "parentage" in a court of law means finding and establishing the identity of the child’s parents. Normally a paternity lawsuit begins with one of the parents or party filing a "Complaint to Establish Parental Relationship" in the court. This party filing the complaint is called the "plaintiff" and the other party against whom the complaint is filed is called the "defendant". As in a dissolution proceeding, this complaint also ends in a judgment being meted out by a court of law. Such a judgment would normally contain orders pertaining to each and every issue raised in the case. The judgment can be a result of a trial, by default or by mutual agreement by the parties involved.

The court may also pass out temporary orders for certain parentage actions during the tenure of the case. After the issue of parentage is addressed and established, other issues like support, child custody and visitation are taken into consideration and handled under the same laws as applicable to a dissolution proceeding.

For example, California law authorizes blood tests in many cases where the parentage of a child is under dispute. Both alleged parents and the child are required to submit themselves to these blood tests. If any of the alleged parents refuse to submit to blood tests, the court has the authority to rule the issue of parentage against the party. However, in certain cases blood tests do not form the admissible evidence due to the statutory presumption of parentage. If the mother in a paternity lawsuit is already married and living with her husband during the conception stage, the court of law conclusively presumes the child to be the child of that marriage.

Similarly, a father who has voluntarily attested his signature on a parentage declaration at the hospital during child birth is conclusively presumed as the father of the child. These presumptions however, may be rebutted in some cases if the presumption can be challenged within three years from the date of declaration.