Shiftwork, regarded as a significant occupational stressor, has become increasingly prevalent across a wide range of occupations. The adverse health outcomes associated with shiftwork are well documented. Shiftwork is an integral part of law enforcement, a high-stress occupation with elevated risks of chronic disease and mortality. Sickness absence is an important source of productivity loss and may also serve as an indirect measure of workers' morbidity. Prior studies of shiftwork and sickness absenteeism have yielded varying results and the association has not been examined specifically among police officers. The objective of this study was to compare the incidence rate of sick leave (any, ≥3 consecutive days) among day-, afternoon-, and night-shift workers in a cohort of police officers and also examine the role of lifestyle factors as potential moderators of the association. Participants (N=464) from the Buffalo Cardio-Metabolic Occupational Police Stress (BCOPS) study examined between 2004 and 2009 were used. Daily work history records that included the shift schedule, number of hours worked, and occurrence of sick leave were available for up to 15 yrs starting in 1994 to the date of the BCOPS study examination for each officer. Poisson regression analysis for ungrouped data was used to estimate incidence rates (IRs) of sick leave by shift, and comparison of IRs across shifts were made by computing incidence rate ratios (IRRs) and their 95% confidence intervals (CIs). Sick leave occurred at a higher rate on the night shift (4.37 per 10,000 person-hours) compared with either day (1.55 per 10,000 person-hours) or afternoon (1.96 per 10,000 person-hours) shifts. The association between shiftwork and sickness absence depended on body mass index (BMI). For overweight individuals (BMI≥25 kg/m2), the covariate-adjusted incidence rate of sick leave (≥1 day) was twice as large for night-shift officers compared with those working on the day (IRR=2.29, 95% CI: 1.69-3.10) or afternoon (IRR=1.74, 95% CI: 1.29-2.34) shift. The IR of three or more consecutive days of sick leave was 1.7 times larger for those working on night shift (IRR=1.65, 95% CI: 1.17-2.31) and 1.5 times larger for those working on afternoon shift (IRR=1.50, 95% CI: 1.08-2.08) compared with day shiftworkers. For subjects with normal BMI (<25 kg/m2), the incidence rates of sick leave did not differ significantly across shifts. In conclusion, shiftwork is independently associated with sickness absence, with officers who work the night shift having elevated incidence of sick leave. In addition, overweight officers who work the night shift may be at additional risk for sickness absence.