Study Design <p>Multicenter clinical trial.</p> Objectives <p>Timed walking tests are commonly used in clinical and research settings to evaluate walking function in people with spinal cord injury (PwSCI), but they usually do not capture the people’s subjective walking experience. The 12-item Multiple Sclerosis Walking Scale (12-WS) is widely used to assess self-perceived walking ability in people with multiple sclerosis (PwMS), but no comparable tool exists for SCI. This study aimed to assess the reliability and validity of the 12-WS in people with cervical or thoracic incomplete SCI (PwiSCI).</p> Setting <p>Balgrist University Hospital, Zurich, Switzerland; Swiss Paraplegic Centre Nottwil, Switzerland.</p> Methods <p>In this clinical trial, 67 PwiSCI (more than 6 months post-injury, AIS C/D) completed the 12-WS and different clinically established gait assessments. Participants completed the 12-WS a second time within a maximum interval of 8 weeks. Results were compared to a cohort of 22 PwMS.</p> Results <p>The test–retest reliability of the 12-WS was excellent (ICC = 0.91; p &lt; 0.001). Internal consistency was high (Cronbach’s Alpha α = 0.95). SEM and MDC95 were 6.5 and 18.1%, respectively. Strong correlations were found with all gait assessments (ρ = ± 0.62&#xa0;to ± 0.67; p &lt; 0.001), except for two items (running and cognitive effort), which showed weaker associations. Results for iSCI were consistent with those for the MS cohort.</p> Conclusions <p>The 12-WS is a reliable and valid patient-reported outcome measure for evaluating walking function in PwSCI. It complements objective gait assessments and supports a comprehensive evaluation of walking function.</p>