The Kentucky senator edged out Florida Sen. Marco Rubio with 25 percent of the vote. Rubio got 23 percent.
Paul's straw poll victory capped the conference in Maryland. The unscientific poll is considered one way to gauge where the conservative base stands on potential Republican nominees for the White House.
Paul has said he's "seriously considering" a presidential run.
Paul and Rubio topped a pool of nearly two dozen governors and elected officials who paraded through the ballroom stage over three days. There were passionate calls for party unity, as the party's old guard and a new generation of leaders clashed over the future of the wayward Republican Party.
First-term Wisconsin Gov. Scott Walker, who placed sixth in the straw poll, on Saturday encouraged Republicans to be aggressive but warned them to focus on middle-class concerns: "We need to be relevant."
Later in the day, the party's 2008 vice presidential nominee, former Alaska Gov. Sarah Palin, mixed anti-Obama rhetoric with calls for a more inclusive GOP: "We must leave no American behind," she said after likening Washington leadership to reality television.
The poll victory offers little more than bragging rights for Paul, who is popular with the younger generation of libertarian-minded conservatives who packed the conference in suburban Washington. Nearly 3,000 people participated in the online survey and more than half were younger than 26.
Paul's father, former Texas Rep. Ron Paul, won the poll in 2010 and 2011, while presidential nominee Mitt Romney took the honor last year.
The Associated Press contributed to this report.