Perry endorsed Gingrich, a former House speaker, after dropping out of the race himself Jan.19, but he switched his allegiance Wednesday to Romney, a former Massachusetts governor, CNN reported.
"Mitt Romney has earned the Republican presidential nomination through hard work, a strong organization and disciplined message of restoring America after nearly four years of failed job-killing policies from President Obama and his administration," Perry said in a statement. "So today I join the many conservative Republicans across the nation in endorsing Mitt Romney for president and pledge to him, my constituents, and the Republican Party than I will continue to work hard to help defeat President [Barack] Obama."
Perry's pledge came after news Gingrich would step out of the race next week.
Perry ended his campaign in January following a disappointing finish in the Iowa caucuses and an unfavorable standing in South Carolina.
"We've had our differences, which campaigns will inevitably have, and Newt is not perfect, but who among us is?" he said at the time in Charleston, S.C.