Low-power complementary organic circuits need to combine p-channel organic field-effect transistors (OFETs) and n-channel OFETs, which are based on p-type and n-type organic semiconductors, respectively. Unfortunately, the performance of n-type organic semiconductors still lags behind that of p-type organic semiconductors. In this work, the performance of solution-processed n-type OFETs was improved via a facile effective route, by blending a p-type organic semiconductor into the n-type polymer semiconductor. The effect of the p-type organic semiconductor additive on the morphology and charge transport was systematically investigated. It showed that the mobility, on/off ratio and stability of the n-type OFETs were significantly improved with incorporation of the p-type semiconductor. The p-type organic semiconductor functioned as a trap center for minority holes and decreased the trap density of the dielectric surface, resulting in an enhancement of the OFET performance. Moreover, blending with an appropriate amount of p-type organic semiconductor also benefited to reset polymer semiconductors stacking order into the direction that promoted charge transport. However, excess p-type semiconductor addition deteriorated the n-channel characteristics due to the formation of a percolation network, providing a pathway for hole transport. To the best of our knowledge, this is the first report about improving the performance of n-type polymer transistors by simply blending with a p-type organic semiconductor.