Finnegan hit Johnson in the mouth at the line of scrimmage and Johnson ripped Finnegan's helmet off. Johnson threw him to the ground as his helmet came off and the receiver punched him at least twice in the head and face.
The two had been pushing and jawing earlier in the game and Johnson has called Finnegan's antics annoying in the past.
Johnson was escorted off the field while Finnegan remained on it before the referees announced that both players were ejected.
The Texans led 17-0 at the time of the ejections.