Objective: This study aims to validate an instrumented dual-task (DT) assessment procedure based on smartphone-embedded sensors. Data processing algorithms were developed to extract relevant features, and ice hockey players were evaluated. Participants: In total, 114 Swiss elite ice hockey players. Design: Experimental study. Main Measures: Participants performed DT tests regularly during the season and within the days following a diagnosed concussion. The DT test consisted of static balance and self-paced walking, combined with counting backward by 3. In total, 265 DT tests were performed, including 38 tests between 1 day and 2 weeks after the 13 diagnosed concussions. Results: Cognitive abilities during gait were mainly affected after a concussion. A DT performance metric was defined based on features significantly associated with worsening DT performance after the concussion (P < .001, effect size d = 1.50). Finally, a model was proposed to estimate the risk of concussion based on a DT test outcome. Conclusion: DT assessments can detect residual cognitive impairments even after other clinical symptoms have resolved. These tests offer medical staff objective insights, facilitating informed decision-making during the return-to-play process