With 77% of the vote, Cuellar had 56.9% and Republican Cassy Garcia had 43.1%, according to the NBC News Decision Desk.
Garcia was one of three Republican Latinas running in South Texas congressional races hoping to cut into the region’s Latino support for Democrats.
Cuellar, a centrist Democrat, has long been further to the right of his party but has said he reflects his district, which is heavily Hispanic but more conservative on issues of abortion, the border and guns.
Cuellar survived a close Democratic primary after the FBI raided his home and after he cast the lone Democratic vote against legislation that would codify federal protection for access to abortion. He has criticized Biden administration policies on immigration and criticized Garcia for her past criticisms of President Barack Obama's health care law, known as Obamacare.