INTRODUCTION: Although there is growing literature supporting the implementation of backward walking as a potential rehabilitation tool, moving backwards may precipitate falls for persons with Parkinson's disease. We sought to better understand interlimb coordination during backward walking in comparison to forward walking in persons with Parkinson's disease and healthy controls. METHODS: We assessed coordination using point estimate of relative phase at each participant's preferred walking speed. RESULTS: Persons with Parkinson's disease demonstrated impaired interlimb coordination between the more affected arm and each leg compared to controls, which worsened during backward walking. CONCLUSION: For those with Parkinson's disease, inability to output smooth coordinated movement of the more affected shoulder may impair coordination during forward and, especially, backward walking. Our findings provide new information about backward walking that can allow clinicians to make safer, more effective therapeutic recommendations for persons with Parkinson's disease.