OBJECTIVES: Pay-it-forward incentives effectively promote hepatitis B virus (HBV) and hepatitis C virus (HCV) testing among men who have sex with men (MSM) by offering free testing and donation opportunities. This study aims to explore the interaction between pay-it-forward incentives and recreational drug use on HBV and HCV testing uptake among Chinese MSM. METHODS: We pooled data from two pay-it-forward studies that aimed to promote dual HBV and HCV testing among MSM in Jiangsu, China. We explored factors associated with hepatitis testing uptake in the two study groups and examined the interaction between pay-it-forward incentives and recreational drug use on hepatitis testing uptake. RESULTS: Overall, 511 MSM participated in these two studies, with 265 participants in the pay-it-forward incentives group and 246 participants in the standard-of-care group. Among these participants, 59.3% in the pay-it-forward incentive group and 24.8% in the standard-of-care group received dual HBV and HCV testing, respectively. In the pay-it-forward incentives group, participants who used recreational drugs in the past 12 months (adjusted OR (AOR)=1.83, 95% CI 1.09 to 3.06) were more likely to receive dual HBV and HCV testing, compared with those who never used recreational drugs, whereas in the standard-of-care group, those who used recreational drugs were less likely to receive dual HBC and HCV testing (AOR=0.38, 95% CI 0.18 to 0.78). MSM with higher community connectedness (AOR=1.10, 95% CI 1.00 to 1.21) were also more likely to receive hepatitis testing with pay-it-forward incentives. There was a synergistic interaction on both the multiplicative (ratio of ORs=4.83, 95% CI 1.98 to 11.7) and additive scales (the relative excess risk of interaction=2.97, 95% CI 0.56 to 5.38) of pay-it-forward incentives and recreational drug use behaviours on dual HBV and HCV testing uptake among MSM. CONCLUSION: Pay-it-forward incentives may be particularly useful in promoting hepatitis testing among MSM who use recreational drugs.