The study examined the effect of dietary supplements of sodium selenite (SS), selenium-enriched yeast (Sel-Plex®, SP) and selenium-enriched alga Chlorella (SCH) on growth traits, carcass analysis, selenium (Se) content in breast meat, glutathione peroxidase (GSH-Px) activity in breast and thigh meat and liver of chickens. Chickens were fed a diet supplemented with 0 (control), 0.15 or 0.30 mg of Se/kg. Selenium addition influenced body weight at 21 (P ≤ 0.001) and 35 (P ≤ 0.05) days of age. The Se content in breast muscle was increased (P ≤ 0.001) by both the lower and higher Se concentration in the form of SP (0.6 and 0.85 mg/kg dry matter) and SCH (0.6 and 0.82 mg/kg dry matter) in comparison with the control (0.31 mg/kg dry matter). A significant increase (P ≤ 0.001) was ascertained even in SS treatments, but no significant differences were found between both levels. The Se source and level, including SS, significantly (P ≤ 0.001) influenced the GSH-Px activity in breast and thigh meat.