Objective: To document the effects of underwater treadmill training (UTT) on leg strength, balance, and walking performance in adults with incomplete spinal cord injury (iSCI). Design: Pre-test and post-test design. Setting: Exercise physiology laboratory. Participants: Adult volunteers with iSCI (n = 11). Intervention: Participants completed 8 weeks (3 × /week) of UTT. Each training session consisted of three walks performed at a personalized speed, with adequate rest between walks. Body weight support remained constant for each participant and ranged from 29 to 47% of land body weight. Increases in walking speed and duration were staggered and imposed in a gradual and systematic fashion. Outcome measures: Lower-extremity strength (LS), balance (BL), preferred and rapid walking speeds (PWS and RWS), 6-minute walk distance (6MWD), and daily step activity (DSA). Results: Significant (P < 0.05) increases were observed in LS (13.1 ± 3.1 to 20.6 ± 5.1 N·kg ), 6MWD (97 ± 80 to 177 ± 122 m), and DSA (593 ± 782 to 1310 ± 1258 steps) following UTT. Conclusion: Physical function and walking ability were improved in adults with iSCI following a structured program of UTT featuring individualized levels of body weight support and carefully staged increases in speed and duration. From a clinical perspective, these findings highlight the potential of UTT in persons with physical disabilities and diseases that would benefit from weight-supported exercise.