ObjectivesWalking impairments are common in individuals with multiple sclerosis. Trunk control is a prerequisite for walking; however, knowledge regarding whether core stability and balance training influence walking is limited. This study aimed to investigate the immediate and long‐term effects of a group‐based, individualized, comprehensive core stability and balance intervention (GroupCoreDIST) compared with those of standard care on walking.MethodsThis assessor‐blinded, prospective randomized controlled trial included 80 participants (Expanded Disability Status Scale scores 1–6.5) randomly allocated to GroupCoreDIST, conducted in groups of three for 60 min three times per week for 6 weeks (18 sessions) or standard care (n = 40/40). One participant attended no posttests, leaving 79 subjects for intention‐to‐treat analysis. The assessments were performed at baseline and at Weeks 7, 18, and 30. Outcomes included the 2‐min walk test (2MWT), 10‐m walk test‐preferred/fast/slow speed (10MWT), Multiple Sclerosis Walking Scale‐12 (MSWS‐12), Patient Global Impression of Change‐walking (PGIC‐walking), Rivermead Visual Gait Assessment (RVGA), and ActiGraphsWgt3X‐BT activity monitors (ActiGraph). The statistical analyses included repeated‐measures mixed models performed in IBM SPSS Version 24.ResultsThere were no significant between‐group differences in the outcome measurements at baseline. The mean differences between groups were significant at all follow‐up time points in favour of GroupCoreDIST for the 2MWT, 16.7 m at 7 weeks (95% CI [8.15, 25.25], 15.08 m at 18 weeks (95% CI [6.39, 23.77]) and 16.38 m at 30 weeks (95% CI [7.65, 25.12]; and the PGIC‐walking, 0.89 points at 7 weeks (95% CI [1.34, 0.45]), 0.97 points at 18 weeks (95% CI [1.42, 0.52]), and 0.93 points at 30 weeks (95% CI [1.39, 0.48]; all p ≤ .001). The 10MWT‐fast speed and the MSWS‐12 showed significant between‐group differences at 7 and 18 weeks and the RVGA at 7 weeks. No between‐group differences were found regarding activity level (ActiGraph) or the 10MWT‐preferred or slow speed.ConclusionCompared with standard care, GroupCoreDIST significantly improved walking immediately after the intervention for up to 24 weeks of follow‐up.