While many companies outsource their logistics functions, creating a collaborative relationship with third-party logistics service providers remains a challenge. The current study explores the effects of often overlooked human factors in this context. Data on buyer perspectives were collected in China. The analysis results suggest that buying firm's top management championship, supplier firm's designated employees, and the buyer-seller personal relationships (i.e. Guanxi) at different levels, all have significant impacts on inter-firm collaboration, which in turn enhances the buying firm's logistics performance.