Laser-induced fluorescence and crossed-beam optical pumping and probing techniques were used to study the cross sections of collisional mixing deactivation of electronically excited copper atoms (2P3/2, 2P1/2, 2D3/2, and 2D5/2) in various buffer gases. The cross sections for total deactivation of metastable status (2D5/2, and 2D3/2) to the ground state by the collision partners He, Ne, Ar, H2, D2, and N2 at 1450 °C are less than 10−20 cm2. Cross sections for the collisional mixing of 2D5/2 and 2D3/2 levels are more than an order of magnitude larger. However, collisional mixing of the 2P3/2 and 2P1/2 levels by the buffer gases does take place more rapidly with cross sections in the range of 10−16 cm2. The cross sections for total deactivation of Cu(2D5/2) to ground state, collisional mixing of the 2P3/2,1/2 levels, and collisional mixing of the 2D5/2,3/2 levels by atomic Cu at 1450 °C are 4.8×10−17, 8.7×10−15, and 1.7×10−15 cm2, respectively.