BACKGROUND AND OBJECTIVES: There is increasing acknowledgment that loneliness is associated with neighborhood characteristics in addition to individual characteristics. We use four waves of geocoded data to examine longitudinal associations between neighborhood characteristics and loneliness of older adults. RESEARCH DESIGN AND METHODS: We draw on "person-environment fit" theory, utilizing individual assessments of neighborhoods, while also creating aggregate assessments by combining responses from other respondents from the same geographic area to test associations with loneliness. RESULTS: Random-effects models demonstrate that both individual and aggregate assessments of neighborhoods are related to loneliness, however, in models that include control variables, the associations between aggregate assessments of neighborhood and loneliness were attenuated. Fixed-effects models show only individual assessments of the neighborhood are associated with variations in loneliness. DISCUSSION AND IMPLICATIONS: Consistent with the "person-environment fit" theory, loneliness appears more sensitive to individual assessments of the neighborhood, irrespective of others' assessments. Our findings point to the subjective nature of loneliness and suggest that measures to reduce loneliness should focus on understanding and addressing individual perceptions of neighborhoods, emphasizing the importance of promoting age-friendly environments.