The 24-year-old's goal was cancelled out by Brighton's James Wilson, but the draw ensures they cannot be caught for fifth place by Sheffield Wednesday.
Weimann has been out of the goals for a while, with his last league strike for the Rams coming in 2015, back in early November against Cardiff.
This was his fourth goal of the season, and a nod to boss Darren Wassall that he is ready to play a part in the play-offs.
The Austrian forward was sold to Derby by Aston Villa last summer, after an up and down time at the Midlands side, where it became clear he was never going to transform into the regular goalscorer they wanted him to be.
After the season they have had, and realisation they face a tough Championship campaign next year after being relegated, fans became suddenly wistful for his attitude and work rate after seeing him net for Derby.
Here is a look at the reaction to his goal...
Say what you want about Andi Weimann, but he always tried. #avfc— Jordan (@JustJordanFM) May 2, 2016
Dudududu! Andi Weimann. Would love for him to come back to Villa #avfc— Sean Williams (@92Swb) May 2, 2016
Why did we let him go! we can only dream now where we would b had we kept Weimann&he's goals!! Oh yeah 16pts with two extra goals for! #avfc— KINGEIGHTYONE (@KingEightyOne) May 2, 2016
Alot of fans disliked him, but weimann always gave his all for #avfc never gave up for his goal then— Lee Hartford (@LHartford83) May 2, 2016
I'd take Weimann back at Villa— Harry (@mrharrymay) May 2, 2016