Container lines have limited opportunities to differentiate their core service, port-to-port transportation, since it is based on standardization. Strategic alliances reduce the opportunities for differentiation even further because of the vessel-sharing between container lines. The container shipping, therefore, is becoming a commodity-like industry. The literature on commodity markets and other business-to-business markets suggests firms can differentiate themselves through the service attributes other than core offering. With this perspective, this study aims to explore effective service differentiators of container lines against their strategic alliance partners. We conduct a survey research with container lines and freight forwarders in Turkey and perform exploratory and confirmatory factor analyses. We create an inter-quartile display to illustrate differentiability and importance level of each service attribute. The results indicate that customer service and customer relations can be effective differentiators for container lines. This study suggests that more customer-focused business policies of the container lines may help them to develop and sustain their competitiveness in intra-alliance competition.