Two passive back-support exoskeleton (BSE) designs were assessed in terms of muscular activity, energy expenditure, joint kinematics, and subjective responses. Eighteen participants (gender-balanced) completed repetitive lifting tasks in nine different conditions, involving symmetric and asymmetric postures and using two BSEs (along with no BSE as a control condition). Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity (by ~9–20%) and reduced energy expenditure (by ~8–14%). Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. Participants reported lower perceived exertion using either BSE yet raised concerns regarding localized discomfort. Minimal changes in lifting behaviors were evident when using either BSE, and use of both BSEs led to generally positive usability ratings. While these results are promising regarding the occupational use of BSEs, future work is recommended to consider inter-individual differences to accommodate diverse user needs and preferences. •Two passive back-support exoskeletons (BSEs) examined during repetitive lifting.•Both BSEs reduced peak back muscle activity and energy expenditure.•No substantial changes in lifting kinematics observed when using either BSE.•Using both BSEs led to generally positive subjective ratings.•Beneficial effects were task- and gender-specific, and differed between BSE designs.