The aim of the present study was to determine the effects of access to a pasture on growth performance, behavioural patterns, some blood parameters and carcass yield of a slow-growing broiler genotype. A total of 210 one-day-old male chicks of Hubbard ISA Red JA were used in the experiment. At the 84th day, live weight was determined to be lower in the outdoor rearing system (P < .01). Better feed conversion ratio was found in the indoor rearing system (P < .01). The behaviour of the broilers was compared by observing the behaviour of three randomly selected marked birds on video tape. Eating, drinking, preening, spot pecking, feather pecking, walking-standing and resting-lying were monitored. Broilers from the outdoor rearing system group showed more preening, drinking, spot pecking, walk-stand and feather pecking behaviours as a result of increasing activity. Ratio of breast and thigh (carcass weight%) was higher, whereas abdominal fat was lower in the outdoor group. As a result of this study, access to a pasture improved the behaviours of broilers.