An unprecedented eastern Pacific cooling along with the strengthening of Pacific trade winds since the late 1990s is considered as a pronounced contributor to the slowdown in global surface warming. Recent studies have demonstrated that the Atlantic sea surface temperature (SST) warming trend and the corresponding trans-basin (Atlantic-Pacific) teleconnection are key drivers to the observed eastern Pacific cooling. Although the Atlantic warming is well captured in the CMIP5 models, most simulations failed to reproduce the eastern Pacific cooling or underestimated the magnitude. Here, we investigate a hypothesis that common model mean state (SST) bias of state-of-the-art models (the multi-model ensemble mean of CMIP5 models) may partly account for discrepancies between the observed and simulated Pacific La Niña-like cooling. Targeted model simulations are then performed to investigate the Pacific response to the observed Atlantic warming trend under various mean SST backgrounds. Model results suggest that simulations with a mean SST bias in both Pacific and Atlantic leads to an underestimated eastern Pacific cooling. Effects of the Pacific and Atlantic mean state bias explains ~35% and ~25%, respectively, of the total tropical Pacific variance in response to Atlantic warming. This result suggests that reducing model mean state bias may significantly contribute towards improving simulations of the Pacific decadal variability and trans-basin teleconnections.