The Fight Club star has long been an activist for gay rights and he famously stated he would not marry Jolie until everybody in the U.S. has the equal opportunity to wed.
Pitt recently donated $100,000 (£62,000) to the Human Rights Campaign (HRC) in support of the organisation's crusade for gay marriages in Maine, Maryland, Minnesota and Washington, and it appears his contribution provided the desired result in Tuesday's elections.
Maine and Maryland became the first states to approve same-sex marriage by popular vote since 1998, while Minnesota voters defeated a proposed constitutional amendment that would ban gay unions in the state.
Results were still pending for Washington as WENN went to press.
HRC President Chad Griffin says, "When the history books are written, 2012 will be remembered as the year when LGBT Americans won decisively at the ballot box. The dreams of millions of fair-minded Americans were realised as discrimination crumbled and equality prevailed."