Two goals in stoppage time from Adam Virgo and Nicky Forster on Tuesday night gave the Seagulls their biggest home win of the campaign to date, following on from Glenn Murray's 34th-minute opener.
Brighton saw their on-loan Newcastle winger Kazenga LuaLua forced off with a leg problem after just 20 minutes but Murray soon had them smiling when he headed in a free-kick from Elliott Bennett at the near post.
Brentford were punished for poor defending as substitute Virgo doubled the lead with a looping header which went in off the far post.
The visitors had substitute Alan Bennett sent off in the fourth minute of stoppage time for deliberate handball, his second booking, and veteran striker Forster stepped up to score Brighton's third goal from the penalty spot.
Brentford, who have scored only nine goals on their travels, rarely threatened although Brighton goalkeeper Peter Brezovan made late saves from substitute Lionel Ainsworth and Kevin O'Connor.