•Firms registered in governors’ hometowns may have more investment expenditures.•Governances’ social identity affects corporate investment.•Chinese-listed firm data reveals the factors influencing hometown favoritism.•Governors prioritize their administrative duties over hometown favoritism.•Increased hometown firm investments lead to investment inefficiency. We investigate the effects of governors’ hometown favoritism on the corporate investments of Chinese listed firms. Exploiting the exogenous distribution of governors’ tenure in a difference-in-differences research design, we find that firms in an incumbent governor's hometown make higher investments by 10.26%. This favoritism effect is more pronounced when any of the following are true about a governor's hometown: has a culture background of high collectivism, has strong clan culture, uses a minor local dialect, or if the governor has strong clan ties. Additional analyses rule out the social ties generated through living or working experiences as an alternative explanation. Neither political connections nor self-interest incentives explain the effects of hometown favoritism. Furthermore, the increased investments are overall detrimental for investment efficiency.Our study contributes to the literature by applying the social identity theory in corporate research and provides novel evidence on how politicians’ social identity affects corporate investment.