Broken down by party affiliation, the poll found 73 percent of Republicans said legalizing same-sex marriage is inevitable, with 72 percent of Democrats and 74 percent of independents agreeing.
Only 31 percent of Republicans, however, say they favor legalizing same-sex marriage. The poll also found that 59 percent of Democrats and 58 percent of independents, respectively, favor same-sex marriage.
The poll's findings come as a number of states seek to pass new laws legalizing gay marriage and the Supreme Court weighs challenges to a California law banning same-sex marriage and the federal Defense of Marriage Act.
The legislature in Illinois, President Obama's home state, last week narrowly failed to pass a measure legalizing same-sex marriage. The measure did not win enough support despite Obama himself expressing support for the proposal.
"And I just want to say for the record it's something that I deeply support," Obama said at a fundraiser in Chicago prior to the vote.
Obama is the first sitting president to publicly back same-sex marriage.
The poll was conducted from May 1-5 among 1,504 adults. The total sample size had a margin of error of plus or minus 3 points.