Background Sports concussion is a risk for players involved in high impact, collision sports. Post-concussion, the majority of symptoms subside within 7–10 days, but can persist in 10–20% of athletes. Understanding the effects of sports concussion on sensorimotor systems could inform physiotherapy treatment. Objective To explore changes in sensorimotor function in the acute phase following sports concussion. Design Prospective cohort study. Methods Fifty-four players from elite rugby union and league teams were assessed at the start of the playing season. Players who sustained a concussion were assessed three to five days later. Measures included assessments of balance (sway velocity), vestibular system function (vestibular ocular reflex gain; right-left asymmetry), cervical proprioception (joint position error) and trunk muscle size and function. Results During the playing season, 14 post-concussion assessments were performed within 3–5 days of injury. Significantly decreased sway velocity and increased size/contraction of trunk muscles, were identified. Whilst not significant overall, large inter-individual variation of test results for cervical proprioception and the vestibular system was observed. Limitations The number of players who sustained a concussion was not large, but numbers were comparable with other studies in this field. There was missing baseline data for vestibular and cervical proprioception testing for some players. Conclusions Preliminary findings post-concussion suggest an altered balance strategy and trunk muscle control with splinting/over-holding requiring consideration as part of the development of appropriate physiotherapy management strategies.