This study examines the impact of granting forest certificates on farmer income. Linear regression and mediating effect models were used to analyze repeated survey data of 505 households in 50 villages in Jiangxi Province in 2017 and 2018. We examined the impacts of granting forest certificates on forestry income and the total income of rural households, taking into account forestland leases. We draw the following conclusions: first, granting forest certificates has a significant positive effect on total household income but not on forestry income. Second, farmers prefer forestland leasing in their behavior. Granting forest certificates can promote forestland lease out, but the effect on forestland lease in is not obvious. Third, granting forest certificates contributes to the increase in total household income through forestland lease out. Our analysis suggests that the government should increase the proportion of granted forest certificates and improve the policies related to the lease of forestland so as to realize an increase in farmer income.