The Federal Constitutional Court in Karlsruhe overturned a ban on Tuesday on so-called "successive adoptions" for gay couples in civil partnerships.
Under the ruling, if one partner has adopted a child, the other partner now has the right to become the adoptive mother or father of that child as well. Until now, they could only adopt their partner's biological child.
This aspect of adoption law had previously only applied to heterosexual couples; a distinction which the Karlsruhe court said went against Germany's basic law and was therefore unconstitutional.
It ruled that same-sex couples could provide for a child as well as couples in a traditional marriage.
"In marriage as in a civil partnership, adoption provides the child with legal security and material advantages in terms of care, support and inheritance law," presiding judge Ferdinand Kirchof told the court.
The ruling followed a legal challenge from a woman who was forbidden from adopting a Bulgarian-born child whom her female partner had adopted.
Tuesday's decision does not alter legislation, however, which forbids same-sex couples jointly adopting a child. They may still only adopt the same child on an individual basis.
Germany legalized civil partnerships in 2001, but in spite of recent rulings in Britain and France, has not yet moved to allow same-sex marriage.
ccp/kms (dpa, AFPD)