Forest had the chance to make a perfect start when they were awarded an early penalty after Pervis Estupinan clumsily fouled Neco Williams.
But Jason Steele produced a big save to deny Johnson’s spot-kick and the hosts missed their chance.
Brighton took the lead in the 38th minute as they capitalised on poor handling from Keylor Navas.
The Chilean goalkeeper palmed Solly March’s shot straight out into the danger zone and Facundo Buonanotte celebrated his first Premier League start with the easiest of tap-ins.
Forest levelled deep into first-half injury time as Pascal Gross put through his own net when he tried to clear Renan Lodi’s cross at the near post, ensuring a frantic first half ended 1-1.
Forest took the lead in the 69th minute with a goal out of nowhere as Danilo closed down Moses Caicedo on the halfway line and then raced on to Awoniyi’s pass and slotted into the far corner to send the City Ground wild.
Forest made sure of the points late on when Morgan Gibbs-White converted from the spot after Lewis Dunk had handled from a corner.
Here’s how the Albion players rated at the City Ground...
1.
Brighton and Hove Albion struggled match Nottingham Forest's intensity at the City Ground Photo: Clive Mason
2. Jason Steele 7
What a penalty save to deny Brennan Johnson. No chance with the first goal as it took a huge deflection of Pascal Gross. The second was a very tidy finish and the third saw him beaten by a penalty Photo: GEOFF CADDICK
3. Pascal Gross 6
Slotted in at right back once more and Brighton missed his presence in midfield. Defended well and joined the attack when he could. Photo: Clive Mason
4. Lewis Dunk 6
Gave a way a penalty with a handball. Felt for the skipper but he timed his jump wrongly as he went up for a header. Otherwise as sound as always. Photo: GLYN KIRK