The victory was only the South Yorkshire side's third success on home soil this season.
Ex-Seagulls striker Mark McCammon did the damage when he met Jonathon Fortes' left-wing cross on 25 minutes to head home the winner.
Rovers dominated the first period and were unlucky not to go ahead ten minutes earlier when centre-back Adam Lockwood saw his close range effort stopped at point blank range by Wayne Henderson.
Brighton came close to levelling soon after McCammon's eventual matchwinner when Tommy Fraser's drive from the edge of the area was blocked by Rovers' impressive debutant in goal Neil Sullivan.
The veteran former Chelsea and Tottenham goalkeeper was signed on loan earlier in the week from Leeds United where he has fallen out of favour following the appointment of Dennis Wise to the Elland Road hot-seat.
With the home side content to sit on their lead, Brighton became more of an attacking force in the second period but could not break through a resolute Rovers back line.
Alex Revell missed a gilt-edged heading opportunity soon after the restart when he really should have tested the keeper.
Shortly afterwards tricky winger Dean Cox curled an effort just past the far post and Revell again went close late on.
Afterwards a relieved Doncaster manager Sean O'Driscoll said: "It was a big win.
"They're the form team and you can see why. We started really well and could have been ahead before the goal - it's always important to score when you're on top.
"It was backs to the wall stuff a bit in the second half but it always looked like we'd score on the break.
"Adam Lockwood was outstanding and Neil Sullivan looked like a Premiership keeper."
Brighton boss Dean Wilkins said his side need to improve how they start games if they are to have any hope of winning promotion back to the Championship.
He admitted: "Maybe it's because we're so young that the players stepping on to the pitch with a little bit of fear. To be honest I just don't know.
"Once we went a goal down after the first half an hour I thought we controlled it from then on.
"But I suppose the biggest disappointment as far as I was concerned was that we simply didn't get enough shots or crosses in during the whole game."
Ex-Seagulls striker Mark McCammon did the damage when he met Jonathon Fortes' left-wing cross on 25 minutes to head home the winner.
Rovers dominated the first period and were unlucky not to go ahead ten minutes earlier when centre-back Adam Lockwood saw his close range effort stopped at point blank range by Wayne Henderson.
Brighton came close to levelling soon after McCammon's eventual matchwinner when Tommy Fraser's drive from the edge of the area was blocked by Rovers' impressive debutant in goal Neil Sullivan.
The veteran former Chelsea and Tottenham goalkeeper was signed on loan earlier in the week from Leeds United where he has fallen out of favour following the appointment of Dennis Wise to the Elland Road hot-seat.
With the home side content to sit on their lead, Brighton became more of an attacking force in the second period but could not break through a resolute Rovers back line.
Alex Revell missed a gilt-edged heading opportunity soon after the restart when he really should have tested the keeper.
Shortly afterwards tricky winger Dean Cox curled an effort just past the far post and Revell again went close late on.
Afterwards a relieved Doncaster manager Sean O'Driscoll said: "It was a big win.
"They're the form team and you can see why. We started really well and could have been ahead before the goal - it's always important to score when you're on top.
"It was backs to the wall stuff a bit in the second half but it always looked like we'd score on the break.
"Adam Lockwood was outstanding and Neil Sullivan looked like a Premiership keeper."
Brighton boss Dean Wilkins said his side need to improve how they start games if they are to have any hope of winning promotion back to the Championship.
He admitted: "Maybe it's because we're so young that the players stepping on to the pitch with a little bit of fear. To be honest I just don't know.
"Once we went a goal down after the first half an hour I thought we controlled it from then on.
"But I suppose the biggest disappointment as far as I was concerned was that we simply didn't get enough shots or crosses in during the whole game."