Paul received nearly 45 percent of the votes cast by California Republican Party members.
Texas Gov. Rick Perry finished second with 29 percent. Former Massachusetts Gov. Mitt Romney came in third.
Those two appear to be pulling away from the pack, but Paul says he's not worried.
"We have strayed away from a good pro-American foreign policy. I think we have strayed from a good, sound monetary policy designed in the constitution, and we certainly haven't followed good fiscal policy. I believe there is a time for change in attitude and a change in direction in this country," Paul said.
Congresswoman Michele Bachmann, who also spoke at the convention, came in fourth.
The convention wraps up Sunday.