INTRODUCTION: Optimal trunk control relies on adequate musculoskeletal, motor, and somatosensory systems that are often affected in people with Alzheimer's disease (AD). Therefore, the aim of this study was to compare trunk control between people with AD and healthy older adults, and investigate the relationship between trunk control and balance, gait, functional mobility, and fear of falling in people with AD. METHODS: The study was completed with 35 people with AD and 33 healthy older adults with matching age and gender. Trunk control was evaluated with Trunk Impairment Scale (TIS); balance with Berg Balance Scale (BBS), Functional Reach Test (FRT), One-Leg Standing Test (OLST) and Five-Repeat Sit-and-Stand Test (5STS); gait with Dynamic Gait Index (DGI); functional mobility with Timed Up and Go (TUG) Test; fear of falling with Falls Efficacy Scale-International (FES-I). RESULTS: BBS, FRT, OLST, and DGI scores were lower and 5STS and TUG Test scores were higher in people with AD compared to healthy older adults (p < 0.05). There was no difference in FES-I score between people with AD and healthy older adults (p > 0.05). TIS was associated with BBS, FRT, OLST, 5STS, DGI, TUG Test, and FES-I (r between - 0.341 and 0.738; p < 0.05 for all). CONCLUSION: Trunk control is affected and related with balance, gait, functional mobility, and fear of falling in people with AD. For this reason, we think that trunk control should be evaluated in the early period, and applications for trunk control should be included in rehabilitation approaches in order to improve balance, gait, functional mobility, and reduce fear of falling.