We developed a human–robot collaborative system in the form of a hybrid cell to perform a collaborative assembly task in a flexible manufacturing setup. We conducted an experiment where 20 human subjects separately performed the assembly task in collaboration with the robot. We observed the collaborative assembly task, reviewed related state-of-the-art research results, interviewed the subjects, relevant researchers and industry experts and thus derived a comprehensive set of assessment and benchmark metrics and methodologies for the collaborative manipulation (co-manipulation) task. The metrics included the core requirements of the task expressed as the key performance indicators (KPI) and the effectiveness of physical interactions between a human collaborator and the robot for the task. The proposed benchmark metrics and methods can help assess and benchmark the overall performance and interactional effectiveness of human–robot collaborative manipulation tasks and systems for various applications such as manufacturing and assembly, logistics and transport, military operations, construction, disaster operations, etc.