The purpose of this study is to investigate the interrelationships between local residents’ perceptions of positive and negative environmental impacts and residents’ place attachment on residents’ support for UNESCO World Heritage sites in Chengdu, Sichuan Province, China. This study also investigates the mediating effect of place attachment in the interrelationships. Data were collected from local residents, after which 520 usable surveys were processed. To investigate our hypotheses, we used descriptive statistics, confirmatory factor analysis, and structural equation modeling. We found that residents’ perceptions of positive and negative environmental impacts exerted significant positive and negative influences, respectively, on place attachment. In addition, residents’ perceptions of positive and negative environmental impacts exerted a positive and negative influence, respectively, on support for UNESCO World Heritage sites in Chengdu. Place attachment was demonstrated to act as a partial mediator between residents’ perceptions of positive and negative environmental impacts and support for UNESCO World Heritage sites.