Because poor sleep quality can reduce quality of life and increase prevalence of illness in workers, interventions are becoming increasingly important for businesses. To evaluate how sleep quality is affected by one-on-one behavioral modification when combined with group education, we conducted a randomized, controlled trial among day-shift white-collar employees working for an information-technology service company in Japan. Participants were randomly allocated to groups receiving either sleep hygiene group education (control group), or education combined with individual sleep modification training (one-on-one group). Occupational health professionals carried out both procedures, and sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). PSQI scores were obtained before and after the intervention period, and changes in scores were compared across groups after adjustments for age, gender, job title, smoking and drinking habits, body-mass index, and mental health as assessed using K6 scores. The average PSQI score for the control group decreased by 0.8, whereas that of the one-on-one group decreased by 1.8 (difference of 1), resulting in a significantly greater decrease in score for the one-on-one group (95% confidence interval: 0.02 to 2.0). These results show that, compared to sleep hygiene group education alone, the addition of individual behavioral training significantly improved the sleep quality of workers after only three months.