The poll, released Friday, showed Americans also have a more favorable opinion of the Democratic Party but have not changed their opinion of Republicans.
The poll -- conducted Nov. 9-12 -- found Obama has a 58 percent favorable rating, up from 55 percent in a poll conducted Nov. 1-2. Romney's favorable rating in the new poll is 50 percent, up from 46 percent Nov. 1-2.
Obama's favorability rating is at its highest point since July 2009, when 66 percent rated him favorable. It is lower than the 68 percent he received immediately after he was elected president in 2008.
Romney's 50 percent rating ties his personal best, recorded in May after he locked up the Republican nomination.
The poll shows a 51 percent favorable rating for the Democratic Party -- the first time the party has had a positive rating since late summer 2009. The party's unfavorable rating is 43 percent.
The Republican Party is viewed negatively by 50 percent of those polled, with 43 percent giving the GOP a positive rating.
The poll was based on telephone interviews with a random sample of 1,009 adults in all 50 U.S. states and the District of Columbia. The margin of error is 4 percentage points.