Tin halide perovskite solar cells (TPSCs) have made great strides recently with an inverted device structure, in with poly(3,4‐ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) has been already widely applied as the hole transport layer (HTL) due to its optical transparency, easy processability, and good mechanical expandability. Nevertheless, the TPSCs still suffer from a severe voltage deficit from the carrier recombination loss and energy‐level mismatch. Herein, hydroxyurea (HYU)‐doped PEDOT:PSS to suppress the voltage loss at the PEDOT:PSS/perovskite interface is applied. It has been revealed that HYU effectively tunes the conductivity and hole mobility of PEDOT:PSS. The interfacial nonradiative carrier recombination is effectively suppressed. The target device shows a 20% increase in the open‐circuit voltage together with an increased power conversion efficiency rising from 8.10% to 10.17%. Therefore, this work provides a feasible strategy to minimize the voltage deficit in TPSCs from the HTL side, which is highly important to further boost the performance of TPSCs.