The Dons secured the win over the English Championship side with a second half goal from striker Adam Rooney.
Aberdeen goalkeeper Langfield was quickly called into action when he got down to make a good save from Kazenga Lua Lua.
And the home team responded when Michael Rose sent a header just over from a Barry Robson corner.
Rooney then had a shot from a tight angle which he lifted over the target during a good spell for the Dons.
Albion raised their game though and Langfield produced another save to turn a free-kick from Danny Holla round the post.
Brighton squandered a better chance after Chris O’Grady played a pass through the Dons defence to Tomer Hemed, but he fired over the bar.
And Brighton were denied again just before the break when Langfield produced his best save of the game to turn away a powerful Lua Lua shot from the edge of the box.
Aberdeen looked sharper after the break as the team prepare for Thursday’s Europa League qualifier against Kairat Almaty in Kazakhstan.
Scott Wright created some space with a neat piece of skill in the middle of the park, and Cammy Smith then crossed for Rooney at the near post but he put the ball wide.
With 15 minutes remaining Smith sent a good delivery into the six yard box and Rooney found the net with a neat back flick.
Aberdeen almost added a second a minute from the end after good play by Wright created space to square the ball to Frank Ross, but his shot was blocked.