Venezuelan Federal Police Chief Wilmer Flores said Valero was arrested after police found the body of his wife, Jennifer Carolina Viera, in a hotel in the city of Valencia.
Flores said Valero left the hotel room around dawn on Sunday and told the hotel's security personnel that he had killed Viera.
Flores told state television that police found three stab wounds on Viera's body. He said Valero was transferred a local police precinct, "where we are headed to take samples needed for the investigation of the case" and to question the boxer.
Valero's lawyer, Milda Mora, did not immediately answer telephone calls seeking comment.
The 28-year-old boxer has been in trouble with the law before.
Last month, Valero was brought up on charges of harassing his wife and threatening medical personnel who treated her at a hospital in the western city of Merida.
Police arrested Valero then following an argument with a doctor and nurse at the hospital, where his wife was being treated for a series of injuries, including a punctured lung and broken ribs.
Valero entered a Venezuelan rehabilitation center under court order on March 28 for treatment of drug and alcohol addiction, Mora said at the time. The boxer's attorney said Viera was injured when she fell down a flight of stairs at the couple's home while checking a water tank located on the roof.
Valero is (was) a national hero in Venezuela; it is unclear how a trial against him will progress. And I should add that he is presumed innocent until proven guilty. Nonetheless, his track record is not good. If he's guilty, he should be locked away for a long, long time.
H/T: BLH. In the comments there, someone is reporting Venezuelan sources stating that Valero has confessed, and will claim self-defense (he's saying his wife attacked him with a knife).
UPDATE: Valero has reportedly hung himself while in prison.