The Texas governor clashed frequently with Romney and even branded the ex-Massachusetts governor a "vulture capitalist" during Perry's own failed run for the Republican presidential nomination.
When he dropped out of the race in January, Perry allied himself with former House speaker Newt Gingrich instead of Romney.
But word that Gingrich plans to give up his presidential bid next week prompted a change of heart for Perry.
In a statement, Perry said Romney earned his status as the presumptive GOP nominee, "through hard work, a strong organization, and disciplined message of restoring America after nearly four years of failed job-killing policies from President Obama."
