Cruz's decision to withhold his endorsement in the crowded GOP primary for the U.S. senate had been one of the biggest talking points of the race.
But on Wednesday, Cruz congratulated Cornyn via Facebook, calling him "a friend and a good man."
The message by Cruz followed a Tweet Tuesday night from Cornyn's chief rival, U.S. Rep. Steve Stockman, calling on his supporters to get behind "the whole Texas GOP ticket."
Cruz, a potential 2016 presidential candidate who holds sway with the anti-establishment wing of the GOP, praised Cornyn as a leader who has "earned considerable respect in the Senate." He added: "We have not agreed on everything, but we have agreed on the vast majority of issues. Together, we're a strong and effective team for Texas."