Chris Hughton’s men looked to be cruising thanks to goals from Kazenga LuaLua and Hemed inside the opening 12 minutes although Ipswich narrowed the deficit through Freddie Sears’ second-half strike.
David McGoldrick’s 64th-minute penalty levelled matters but Brighton restored their lead almost straight away as Hemed headed home LuaLua’s cross to give the visitors a deserved three points.
Brighton started sharply and it did not take long for LuaLua to grab the game’s first goal after he was set clear by Gaetan Bong’s long ball, with the former Newcastle winger firing into the bottom corner after just 10 minutes.
And it was 2-0 two minutes later when Dale Stephens’ inswinging free-kick from the touchline got the briefest of touches from the head of Hemed and nestled in the far corner of Dean Gerken’s goal.
The visitors were well worth their two-goal lead and they should have made it three in the 23rd minute when another Bong long through ball caught the Town defence cold but striker Sam Baldock poked a golden chance just wide.
Sears was Ipswich’s brightest spark in a dismal first-half display and he fired a neatly-worked free-kick just wide in what was the home side’s best moment of the first 45 minutes.
Making two changes at half-time, Ipswich looked brighter in the opening exchanges of the second half but they were still vulnerable at the back and they survived a massive scare when Stephens’ low drive cannoned off the far post.
Ipswich got themselves back in the game when an incisive break involving substitute McGoldrick and Ryan Fraser released Brett Pitman and while his shot hit the post, Sears was on hand to fire home the rebound.
Hemed fired a shot into the side netting after another quick counter attack from the away side before Liam Rosenior and Beram Kayal both went close to adding a third.
Ipswich themselves were posing more of a threat and grabbed the equaliser from the penalty spot when Bruno Saltor brought down Fraser and McGoldrick found the corner from 12 yards.
But parity lasted just 120 seconds as Hemed met LuaLua’s cross to powerfully head past Gerken.
LuaLua came close to adding a fourth after some excellent play by the impressive Sam Baldock while at the other end David Stockdale got a diving hand to Sears’ cross and was fortunate that the rebound fell to a team mate.
Brighton still looked the greater threat and Tommy Smith headed another Hemed header away from his own goal-line while Fraser went close for Ipswich with a shot from 25 yards.