Delhomme worked out with the Texans on Tuesday, along with another retired quarterback, Jeff Garcia. Delhomme will back up rookie T.J. Yates, a fifth-round pick who will start Sunday's game against Atlanta.
Rick Smith, Delhomme's agent, said the 36-year-old Delhomme has been staying in shape and working with racehorses in Louisiana since he was cut by Cleveland in July.
Houston signed Kellen Clemens last week after learning that Schaub will need season-ending surgery on his right foot. Leinart broke his left (throwing) collarbone in Sunday's 20-13 win over Jacksonville.