The film about a fish trying to find his son has now taken a massive $328.7m (£208.5m) in the US, which is more than previous record holder The Lion King.
But the Lion King is still the biggest animated film globally, having taken $780m (£494.8m) in world-wide ticket sales.
The Lion King, made in 1994, also did really well in video sales in the US, selling $55m worth to become the biggest seller ever.
Finding Nemo could also top that figure when it comes out to buy in America in November, but since DVDs now sell loads too, it won't beat the video record.
Finding Nemo comes to UK cinemas in October.