The present study was carried out to compare the efficiency of different selenium (Se) sources [sodium selenite (SS), Se enriched yeast (Sel-Plex) and Nano-Se] on productive performance, lipid peroxidation, antioxidative status and immunity function of local chickens strain exposed to summer condition (high ambient temperature). One hundred and twenty birds, were randomly divided into 4 treatments: (1) control (basal diet without any supplementation of selenium), (2) SS (basal diet + 0.3 mg Se as SS / kg diet); (3) basal diet + 0.3 mg Nano-Se/ kg diet (Nano-Se); and (4) basal diet + 0.3 mg organic Se/ kg diet (Sel-Plex). The experimental diets are given to birds from 30 to 42 wk of age. Under hyperthermia, dietary 0.3 ppm Sel-Plex or Nano-Se improved feed conversion (g feed/g egg mass), egg production percentage and egg mass (g/d) (P < 0.05). Supplementing diets with Nano-Se increased total protein and globulin content compared with control diet. While, addition different sources of selenium significantly decreased malondialdehyde (MDA) content compared with treat (1) diet. Interestingly, under rise ambient temperature, the inclusion of 0.3 ppm Sel-Plex or Nano-Se in the chikens diet significantly enhanced the antioxidant enzyme (GSH-Px) activity being greater than 2-folds of the controls.  Chickens fed diet supplemented with Sel-Plex or Nano-Se showed about 1.5-folds increase in seminal plasma (GSH-Px) compared with control diet. Dietary 0.3 ppm Sel-Plex or Nano-Se had a positive significant effect on Phagocytic activity (PA) and Phagocytic index (PI) on high ambient temperature. In conclusion, dietary 0.3 ppm organic Se or Nano-Se enhanced productive performance, antioxidative properties and immunity in chickens reared under heat stress conditions.