The winger, a £1million summer capture from Vicarage Road, struck late in the second half on Tuesday night as the Seagulls came from two goals behind to snatch a point.
Rising star Sean Murray had put Watford ahead with superb free-kick before Troy Deeney made it two from the penalty spot before half-time.
But Inigo Calderon pulled one back and Buckley denied his old side victory while ensuring Brighton avoided a fourth straight defeat.
Boss Gus Poyet swung the axe after Saturday's 6-0 drubbing at West Ham saw their play-off hopes all but disappear.
He made five changes including dropping goalkeeper Peter Brezovan, opting instead to hand a debut to former Manchester City reserve David Gonzalez.
Unfortunately for the Colombian, his first task was to pick the ball out of the back of the net after watching Murray's sixth-minute cracker sail over him.
The Seagulls were behind after just two minutes at the weekend but lasted a little longer this time, and could even have been ahead themselves had recalled striker Craig Mackail-Smith not driven his low shot too close to Tomasz Kuszczak.
However, 30 seconds later Marcos Painter fouled Deeney 25 yards out and Murray stepped up to curl his effort beyond the reach of Gonzalez and into the net.
The 18-year-old midfielder's four goals in March saw him named young player of the month and he now has six in 12 matches - not bad considering he only made his first start of the season in January.
Buckley came agonisingly close to levelling in the 40th minute when his glancing header from Kazenga LuaLua's cross came back off the inside of the post.
And instead of going in level at the break, the Seagulls found themselves two down when Ashley Barnes' rash tackle from behind felled Jonathan Hogg in the area and Deeney stepped up to tuck the penalty past Gonzalez.
Brighton were given hope nine minutes into the second half when captain Calderon charged forward from right-back and lashed the ball past Kuszczak at the second attempt.
Poyet then threw on Vicente Rodriguez in a bid to keep the momentum going and the former Spain international did not disappoint, providing the pinpoint cross from which Buckley tucked in the equaliser 11 minutes from time.