This study deals with the effects of extra oxygen supplementation in high altitude (1700 m) on hatching traits in pheasant (Phasianus colchicus) eggs during the last 4 days of incubation. The hatching eggs were obtained from a 44 weeks old Pheasant flock. All eggs were distributed randomly into one incubator and incubated for 37.6 degrees C and 58% RH 21 days using uniform conditions. At the start of 22nd day of incubation, the eggs were randomly distributed to two experimental hatching cabinets. The temperature and RH were changed as 37.2 degrees C and 90-92%, in both cabinets for the last 4 days of incubation. During the last 4 days of incubation, two oxygen concentrations were added to the cabinets as 19 and 23%, separately. Fertile Hatchability (FH), Internal (IP), External (EP) pipping mortalities and Late Mortalities (LM) of embryos and some supply organ weights of chicks were recorded. The 23% oxygen treatment significantly reduced EP and LM mortalities compared to control group. Increasing oxygen level at this altitude has improved the FH in 23% oxygen treatment group compared to that resulting from 19% oxygen. At hatch, lower liver weights were obtained from 23% oxygen treatment group compared to control group. These findings revealed that fertile hatchability can be improved if oxygen levels elevated at high altitudes during plateau stage of incubation in Pheasant eggs.