The objective of the present experiment was to determine the effects of slaughtering at different ages and the use of a commercial probiotic (115-Biogallinox) in broiler diets on the color properties of carcasses, during the first 24 h following slaughter. Ross 308 male broiler chickens obtained from a commercial hatchery were raised to either 35 or 42 days of age. Chickens were fed with different levels of probiotic (P-0 0.0%, P-1 0.1% and P-2 0.2%) containing Saccharomyces cerevisiae during the experimental period. At the end of the trial all birds were slaughtered and then stored at PC for 24 h. The pH and skin colour of carcasses were determined 1, 3 7, 10, 13, 17 and 24 h after slaughter. Although the use of probiotic and post-mortem ageing time affected the pH (p < 0.01), it was not affected by slaughter age (35 and 42 days) (p > 0.05). The highest pH values occurred in carcasses of broilers fed 0.2% probiotic. The pH values of carcasses decreased with post-mortem ageing time (p < 0.01). Main factors (treatment, slaughter age and post-mortem ageing time) had an effect on colour (L*, a* and b*) values (p < 0.01). L* values of 42d-old slaughter and P2 group were lower than those of 35d-old slaughter and other probiotic groups. The a* and b* values of 35d-old slaughter were lower than those of 42d-old slauhgter. The a* and b* values increased during post-mortem ageing (p < 0.01). It was determined that changing of the colour traits of broiler carcasses was correlated with probiotic, pH and post-mortem ageing time. Also, it was observed that darkness of carcass colour increased as time progressed.