Manual wheelchair users with asymmetrical upper limb function often face significant challenges due to the inefficiencies of conventional propulsion systems, such as the dual-handrim wheelchair. This study evaluates a novel steering-by-leaning (SBL) manual wheelchair system designed to decouple navigation from propulsion, allowing one-handed propulsion while maintaining directional control through upper body movement. Seven participants completed a test course using both a conventional dual-handrim wheelchair and the prototype, each operated with just one hand. Performance was assessed through task completion time, Wheelchair Skills Test scores, and subjective usability ratings. The results demonstrated a significant decrease of 25% (p ≤ 0.001) in completion times and a 30% (p ≤ 0.001) increase in performance scores with the prototype. Additionally, users reported lower perceived difficulty and greater confidence when using the prototype. These findings suggest that the steering-by-leaning mechanism offers a promising alternative for improving mobility and independence in one-handed wheelchair users. Further research is needed to validate these results in larger, more diverse populations, and to improve wheelchair-user fit in steering-by-leaning wheelchairs.