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Objective Firefighters face unique occupational challenges related to their sleep. Even compared to other shift workers, their schedules are unusual and complicated and sleep debt is prevalent among them. Considering the complexity of firefighter shift schedules and the population’s risk of sleep debt, further scientific exploration into the impacts of their shift schedules on cognitive fatigue is warranted. This pilot study estimated the hazard of cognitive fatigue across firefighter shift schedules and identified demographic risk factors.Material and Methods A total of 44 career firefighters were recruited from a full-time suburban fire department in Minnesota, USA. Using the Fatigue ScienceTM Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) ReadiWatch, participants’ sleep was tracked over the course of 90 days, including sleep quantity, quality, nap status, and fragmentation. The SAFTE ReadiScore System (RSS) predicted cognitive fatigue scores over time, ranging from 0-100, with 100 being perfectly rested. Cox regression models were used to measure the hazard of fatigue, including models adjusted for age, sex, marital status, parental status, and chronotype.Results The hazard of fatigue increases over the course of firefighter shifts, with slight recovery after days off. Being female, having an adaptable chronotype, napping during the day, being unmarried, and having no children decreased fatigue, but age was not associated with hazard risk.Conclusion Firefighters are at increased risk of fatigue over the course of a tour of duty and can benefit from restorative sleep on their days off and napping during the day in general. This study is limited by its small, homogenous sample. Future research could elaborate on this pilot study with an increased sample size and compare various firefighter shift schedules.Funding This study was funded by the Midwest Center for Occupational Health and Safety CDC/NIOSH 5T42OH008434-19