He said on ABC's "Good Morning America" Friday the same thing is happening with the issue of marriage that happened with gays' service in the military.
Changes in attitudes by military leaders, those in the service and the public allowed the repeal by Congress of the "don't ask, don't tell" policy that will eventually allow gays to serve openly in the military.
"I think the country's evolving," Biden told "GMA" host George Stephanopoulos. "And I think you're going to see, you know, the next effort is probably going to be to deal with so-called DOMA [Defense of Marriage Act]."
Gay marriage is still not legal in most states.
President Barack Obama recently said, but he still believes in allowing strong civil unions that provide certain protections and legal rights that married couples have.
DOMA, passed by Congress in 1996, was a federal law defining marriage as a legal union between one man and one woman, and allowed for states to withhold recognition of same-sex marriages recognized by other states.
In July one man-one woman provision of the law was declared unconstitutional by a federal judge on equal protection grounds.