The current study was designed to investigate the effects of the biological age (BA) of broiler chickens and feed access at hatching on growth performance, serum biochemical parameters, and intestinal morphology at slaughter age. A total of 720 chickens (Ross 308) were randomly allocated into 6 treatment groups as follows: 1-475 h of BA with direct feed access, 2-475 h of BA with delayed feed access, 3-489 h of BA with direct feed access, 4-489 h of BA with delayed feed access, 5-503 h of BA with direct feed access, and 6-503 h of BA with delayed feed access. The chickens at 489 h of BA with direct feed access were found to be the heaviest with a value of 167.8 g at 7 d of age, whereas a higher body weight was observed in chickens at 475 and 489 h of BA with direct feed access with a value of 524.3 g at 14 d of age. The highest body weight gain was found with a value of 2527 g in broilers at 489 h of BA with direct feed access. Broilers at 475 h of BA with direct feed access had the worst FCR compared to the other groups. Small intestine morphological characteristics showed alterations for the duodenum, jejunum and ileum. The broilers at 489 h of BA had a higher ratio of villus height and crypt depth than the broilers at 475 and 503 h of BA. It resulted in a decreased turnover of the jejunum and ileum, which meant a lower maintenance demand and subsequently a higher body weight gain of broilers at 489 h of BA with direct feed access. The present findings show that chickens at different BA (475, 489, and 503 h) benefit from feed access in different ways, showing differences in body weight gain, feed efficiency, and small intestine morphological characteristics.