Both Palin and her husband, Todd, pledge their support in a letter to Cruz, who hopes to replace retiring U.S. Sen. Kay Bailey Hutchison.
"Your conservative principles, passionate defense of our Constitution and our free market system come at a time when these cornerstones of our freedom and prosperity are under attack," Palin wrote in the letter, according to the campaign. "Our shared goal isn't just to change the majority in control of the Senate, but to assure principled conservatives like you are there to fight for us."
In a statement, Cruz said he was "humbled and honored" by the endorsement.
"With Governor Palin's support, and the support of tens of thousands of conservatives from all across Texas, we will turn our country around, rein in out-of-control spending and debt in Washington, and restore the Constitution," Cruz said.
Since gaining nationwide prominence after 2008 GOP presidential nominee John McCain picked her as his running mate, Palin has periodically endorsed candidates in various races around the country. In 2010, she endorsed Gov. Rick Perry in his re-election bid against Hutchison. Last month, she endorsed Indiana Treasurer Richard Mourdock, who this week defeated longtime U.S. Sen. Richard Lugar in that state's Republican primary.
Polls have consistently shown Cruz trailing the frontrunner in the Republican race, Lt. Gov. David Dewhurst.
