Objective: To investigate whether the relationship of neighborhood environmental factors with physical activity (PA) is moderated by cognitive functioning in Belgian older adults. Methods: Seventy-one older adults completed validated questionnaires on PA and environmental perceptions, wore an accelerometer, and completed a computerized assessment of cognitive functioning. Moderated linear regression analyses were conducted in SPSS 24.0. Results: Overall cognitive functioning significantly moderated the associations of traffic safety and street connectivity with PA. Detailed analyses showed that these factors were only positively associated with PA in older adults with lower cognitive functioning. In addition, particularly, performance on tests assessing visuospatial and episodic memory moderated these associations. Discussion: Living in traffic-safe neighborhoods with short and many alternative routes might motivate older adults with lower cognitive functioning to be active. As such, the increase in PA might improve their cognitive abilities. This knowledge is crucial for health practitioners to develop effective PA promotion initiatives.