Epidemiological studies have found a consistent inverse relationship between increased body mass index (BMI) and sleep duration. These studies have not controlled for the role that job related factors such as shift work and working hours may have on this relationship. A cross sectional survey of shift and day workers (N=346; 292 males and 59 females) was employed to investigate the association between obesity, job related factors and sleep duration. Mean age for the overall sample was 41.1 yr (± 11.1). Mean BMI was significantly higher in shift workers than in day workers (p<.001). Mean BMI (12.60 h ± 0.41) was also significantly (p<.001) higher in the group working long daily hours followed by medium working hours (10.95 h ± 0.56) and short working hours (8.72 h ± 0.56). Obese individuals worked significantly longer hours (p<.001) and slept 18 min less per day (p<.06) compared to those with a normal BMI. The adjusted odds ratio (OR) indicated the most significant predictor of obesity was long working hours (OR=2.82, CI: 1.10–7.19), followed by being older (OR=2.05, CI: 1.17–3.59) and short sleep duration (OR=1.92, CI: 1.03–3.55). The limitations of the study are discussed.