"We deserved this result," BBC Sport quotes Wagner as saying. "We were second best in everywhere and weren't good enough with the ball.
"We have to be braver and more comfortable on the ball. We made too many unforced errors. It was an unlucky goal that we conceded but we have to be honest West Ham were stronger today."
It is the first time that Huddersfield have been beaten in the Premier League this season following two wins and a draw since their promotion from the Championship.