Cu(In, Ga)Se2 (CIGS) precursor films were electrodeposited on Mo/glass substrates in acidic solutions containingCu2+, In3+, Ga3+, and Se4+ ions at −0.6V (SCE) and pH 1.8. In order to induce recrystallization, the electrodepositedCu1.00In0.81Ga0.09Se2.08 (25.0at.% Cu+20.2at.% In+2.2at.% Ga+52.0at.% Se) precursor films were annealed under a highSe gas atmosphere for 15, 30, 45, and 60 min, respectively, at 500oC. The Se amount in the film increased from 52at.% to62at.%, whereas the In amount in the film decreased from 20.8at.% to 9.1at.% as the annealing time increased from 0 (as-deposited state) to 60 min. These results were attributed to the Se introduced from the furnace atmosphere and reacted withthe In present in the precursor films, resulting in the formation of the volatile In2Se. CIGS precursor grains with a cauliflowershape grew as larger grains with the CuSe2 and/or Cu2-xSe faceted phases as the annealing times increased. These faceted phasesresulted in rough surface morphologies of the CIGS films. Furthermore, the CIGS layers were not dense because the emptyspaces between the grains were not removed via annealing. Uniform thicknesses of the MoSe2 layers occurred at the 45 and60 min annealing time. This implies that there was a stable reaction between the Mo back electrode and the Se diffused throughthe CIGS film. The results obtained in the present research were sufficiently different from comparable studies where therecrystallization annealing was performed under an atmosphere of Ar gas only or a low Se gas pressure.