In the context of the rapid rise of agricultural mechanization in China, this paper examines the impact of household-owned farm machinery and outsourced agricultural machinery services on the land leasing behavior of Chinese relatively large-scale farmers. Based on the CFPS2018 survey data, this study suggests that farm machinery is beneficial for expanding the scale of farms. With increases in household-owned machinery, farmers are more inclined to lease-in land, and they are less inclined to rent-out land. The more agricultural machinery services farmers purchase, the more they tend to transfer-in land and the probability of transfer-out land is lower. However, uneven village terrain can weaken the effects of the two kinds of agricultural mechanization on land leasing. Moreover, this study confirms that household-owned farm machinery and outsourced agricultural machinery services could positively regulate each other's influence on land leasing, indicating that there is a complementary relationship between the two types of agricultural machinery. Further mechanism analyses show that the channels by which household-owned farm machinery and outsourced agricultural machinery services affect land leasing are quite different. The self-purchased machinery of farmers mainly plays a role through labor complementarity effects, while outsourced agricultural machinery services mainly affect land leasing through labor substitution effects. •With increases in household-owned machinery, farmers are more (less) inclined to lease-in (lease-out) land.•The more agricultural machinery services farmers purchase, the more (less) they tend to transfer-in (transfer-out) land.•There is a complementary relationship between household-owned farm machinery and outsourced agricultural machinery services.•Self-purchased farm machinery mainly plays a role through labor complementarity effects.•Outsourced agricultural machinery services mainly affect land leasing through labor substitution effects.