This study aims to propose an assessment tool of port service quality (PSQ) in the context of container transport logistics (CTLs), by taking the perspectives from port users. The CTLs defined in this study are the relevant activities of serving the physical flows of a container box from a point of origin via a container port to a point of destination. To address the ports’ role in collaboration between its channel members in CTLs, the PSQ measures for all port user groups (i.e. common PSQ measures) are selected based on the relevant CTLs activities involved by port, and its users within terminal/port area as well as throughout the CTLs chain. An importance-performance analysis (IPA) is applied as a diagnostic tool to analyse the status quo of Busan Port in CTLs contexts, by comparing the importance and performance (IP) scores against each individual CTLs criterion. The findings from the IPA reveal that port managers and policy makers at the Busan Port should concentrate on six PSQ measures (i.e. SR1, SR4, ITS1, VAS1, VAS4, ICI3) to enhance PSQ in CTLs. However, four measures (i.e. ITS2, ITS3, ITS4, VAS2) are identified as a possible overkill, indicating an area of inefficiency where a remedial action of the cost-cutting decision is necessary. On the other hand, the Busan port shows an outstanding performance on four measures such as SR2, SR3, ICI1 and ICI2. The measures are not only important but also high performance. The study findings provide managerial guidance to port managers in Busan Port, in view of searching for managerial and operational strategies for sustainable port growth.