Background: In 2016, the Ministry of Health, Labour and Welfare established the Health Support Pharmacy Certification System. The certification requirements include a track record of counseling regarding the use of over-the-counter drugs (OTC). Therefore, pharmacists must increase their self-efficacy for counseling. Objectives: To determine pharmacists’ self-efficacy for OTC counseling and related factors. Methods: A web-based survey was conducted. Multivariate analysis was conducted to test the relationship among the mean scores of self-efficacy for OTC counselling for 25 symptoms, pharmacist attributes, years of work, psychosocial factor, job satisfaction, and level of trust from the community and patients. Results: We received responses from 250 people. The overall self-efficacy was 5.8 (SD= 2.4) but varied depending on the symptoms. Self-efficacy was relatively high for allergic symptoms (6.9), cold/influenza (6.9), and constipation (7.1), but relatively low for contraceptive drugs (3.8), palpitation/shortness of breath (4.6), and abnormal taste/smell (4.2). In bivariate analysis, items related to self-efficacy included “age” (Spearman correlation= 0.276, P<0.001), “academic background” (-0.208, P=0.001), “number of years of work” (0.267, P<0.001), “level of trust from the community” (0.155, P=0.014), “level of trust from patients” (0.271, P<0.001), “job satisfaction” (0.236, P<0.001), “role clarity” (0.181, P=0.004), and “positive challenge at work” (0.271, P<0.001). Multivariate analysis indicated that the number of years of work (Standardizing Coefficient: 0.22), trust from patients (0.13), and positive challenge at work (0.25) had a positive effect on self-efficacy. Conclusions: Years of work, recognition that they are trusted by patients, and positive challenge at work were important for the counseling self-efficacy of pharmacists. These results provide implications for pharmacy management and lifelong education strategies to promote self-efficacy in pharmacist counseling.