Unsafe acts have been identified as a major factor of construction accidents. e eory of Planned Behaviour (TPB) has been used to explain the factors influencing unsafe behaviour, by establishing the relationship between attitude, intention, and behaviour. However, the existing research on the relationship between safety attitude and safety behaviour could not fully explain the decisionmaking process of unsafe acts, in that the relationship could be mediated by attitudinal ambivalence, which is caused by conflicting information sources and the social network pressure of peer workers. is research examined whether attitudinal ambivalence was a mediating factor, either fully or partially, in the relationship between safety attitude and safety behaviour by expanding the TPB model. Data were collected from questionnaire survey of 228 construction workers. e results showed that attitudinal ambivalence existed as a partial mediating factor in the relationship between safety attitude and safety behaviour. is paper contributed to the body of knowledge on safety management by recognizing the role of attitudinal ambivalence in construction workers and integrated it into the TPB model. is research will be helpful in providing greater understanding of the dynamic and complex decision-making process of unsafe behaviour given multiple information sources and conflicting environments.