Stress has been acknowledged as one of the aetiologies of female reproductive dysfunction, yet the mechanisms involved are not totally elucidated. Based on the paucity of information on how predator stress (PS) affects oestrous cycle in rats, this study was designed to investigate the effect of predator stress on oestrous cycle in rat. Normal cycling Wistar rats were divided into two groups (n=24 rats/group), namely, Control and PS group. Each group was subdivided into four groups (n=6/group) according to the phases of their oestrous cycle. Stress was induced by exposing rats to cat (predator) for 60 minutes/day for 14 consecutive days. Vaginal cytology was monitored daily to determine phases of the cycle. On the last day of stress exposure, oestrous phase was noted, and then animals were sacrificed by cervical dislocation. Blood was collected through cardiac puncture and centrifuged at 3000rpm for 15 minutes to obtain serum for hormonal analysis. Values are presented as mean±SEM, and analysed by one-way ANOVA. Results revealed significant (P≤0.01) disruption of oestrous cycle by PS which is dependent on the oestrous phase of the rat at the commencement of stress exposure. However, animals that were exposed to predator in their proestrus phase (PS-proestrus) showed sign of recovery from the disruption. In animals exposed to PS, percentage occurrence of diestrus was significantly increased (P≤0.01) regardless of the phase of first exposure compared with control animals. Hormonal analyses revealed that there was a significant increase in prolactin concentration (6.50±0.33ng/ml, P≤0.01) in stressed animals sacrificed on estrus phase compared with diestrus phase (3.08±0.26ng/ml, P≤0.01) and respective phases in control (3.45±0.41ng/ml vs. 5.05±0.83ng/ml, P≤0.01). Progesterone concentration was significantly reduced in animals sacrificed on estrus phase (10.67±2.99ng/ml, P≤0.01) when compared with diestrus phase (34.67±4.23ng/ml, P≤0.01) and respective phases in control (24.33±1.93ng/ml and 29.58±3.52ng/ml, P≤0.01). Estradiol was significantly (P≤0.01) reduced (26.83±2.41pg/ml and 23.50±2.81pg/ml) in stressed group compared with control (40.17±3.26pg/ml and 31.83±2.04pg/ml) at estrus and diestrus phases respectively. Similarly, luteinizing hormone (LH) was reduced in both phases (19.33±1.87mIU/ml and 16.33±1.87mIU/ml, P≤0.01) in stressed group compared with control (31.83±2.41mIU/ml and 21.00±2.28mIU/ml). Follicle stimulating hormone (FSH) was increased in stressed animals sacrificed on diestrus (34.67±2.45mIU/ml, P≤0.01) compared with those on estrus (7.33±1.26mIU/ml) and corresponding phases in control (13.17±2.17mIU/ml and 23.00±2.38mIU/ml). This study shows that PS disrupts oestrous cycle and altered the hormonal levels depending on the phase of oestrous cycle at first exposure.