Weimann, who joined Derby in the summer transfer window, was on target for the Rams in the 1-1 draw with 10-man Brighton & Hove Albion away from home in the Championship.
The 24-year-old Austria international, who can play as a forward or as a winger, found the net in the 71st minute at the American Express Community Stadium.
James Wilson rescued a point for the Seagulls with the equaliser in the fifth minute of injury time.
Weimann has taken to Twitter to express his delight at his goal and at Derby’s overall performance against Brighton.
Derby will take on Ipswich Town at the iPro Stadium in the Championship next weekend.
It is a meaningless game for the Rams, who have already booked their place in the playoffs.
However, Derby should try to win the match, as it is going to help them maintain momentum going into the playoffs.