The aim of the present study is to investigate the associations of fear of falling, cognitive characteristics, and sleep quality with gait kinematics in physically active and inactive older adults. This study is an analytical, cross-sectional, comparative-correlational study that will be conducted among community-dwelling adults aged 60 years and older in Tehran. Participants will be selected using convenience sampling and categorized into two groups based on their level of physical activity: physically active and inactive older adults. Fear of falling, cognitive function, cognitive reserve, sleep quality, and physical activity will be assessed using the Short Falls Efficacy Scale-International (Short FES-I), Montreal Cognitive Assessment (MoCA), Cognitive Reserve Index questionnaire (CRIq), Pittsburgh Sleep Quality Index (PSQI), and Physical Activity Scale for the Elderly (PASE), respectively. Gait kinematics will also be assessed using the markerless OpenCap system during walking along a straight 10-meter path at the participant’s preferred walking speed. The data will be analyzed using descriptive statistics, tests of data distribution, correlation analysis, and multiple linear regression. The findings of this study may contribute to a better understanding of the associations of psychological, cognitive, and sleep-related factors with gait patterns in physically active and inactive older adults and help identify factors associated with changes in gait kinematics.