The studio ceased operations in 2000, when they were set to do the animation production on WXIII: Patlabor the Movie 3.
In 1998, the company released Serial Experiments Lain receiving the Excellent Award from the animation division of the Japan Media Arts Festival.
Later in December 2000, animators Shojiro Abe and Takeshi Baba established A.C.G.T, a subsidiary of OB Planning Co., Ltd. Triangle Staff ceased all operations in December 2000, though the exact reason and time of it shutting down remain unknown.
After the discontinuation, the name of the company was still shown on the copyright trademark and the staff list embedded in the studios' productions.
Production was later taken over by Madhouse and was released in theaters on March 30, 2002 (though Triangle Staff's involvement would be acknowledged in the film's end credits).