We use detailed information on individual absent spells of all employees in 4140 firms in Denmark to show large differences in average absenteeism across firms. Using employees who switch firms, we decompose days absent into an individual component (e.g., motivation, work ethic) and a firm component (e.g., incentives, corporate culture). We find the firm component explains 50%–60% of the difference in absenteeism across firms, with the individual component explaining the rest. We present suggestive evidence of the mechanisms behind the firm effect with family firm status and concentrated ownership strongly correlated with decreases in absenteeism. We also analyze the firm characteristics that correlate with the individual effect and find that firms with stronger career incentives attract lower-absenteeism employees.