Despite continued interest in neighborhood correlates of physical activity, few self-report questionnaires exist that capture neighborhood-based physical activity. Furthermore, there is little evidence about the measurement validity of self-report measures of neighborhood-based physical activity. Notably, self-reported neighborhood physical activity has not been validated against combined accelerometer and global positioning system (GPS)–assessed physical activity. Thus, the purpose of this study was to estimate the concurrent validity of a recently adapted tool for capturing self-reported neighborhood-based physical activity (i.e., the Neighborhood International Physical Activity Questionnaire; N-IPAQ). Adults (n = 75) from four Calgary (Alberta, Canada) neighborhoods wore an accelerometer and GPS monitor for 7 consecutive days after which they self-reported their physical activity from the past week using the N-IPAQ. Bland-Altman plots and Spearman correlations estimated the concurrent validity between N-IPAQ and accelerometer/GPS physical activity (estimated for the administrative boundary, 400-m and 800-m radial buffers). The mean (95% Confidence Interval [CI]) difference between the N-IPAQ and accelerometer/GPS estimated total daily minutes of physical activity differed for the 400-m (1.9 min, −26.2 to 29.9), 800-m (10.6 min, −16.0 to 37.1), and administrative boundary buffers (14.7 min, −11.5 to 41.0). The strongest Spearman correlations were found between the N-IPAQ and 800-m radial buffer accelerometer-captured vigorous-intensity physical activity (r = .41 [95% CI: .18 to .60]), and the N-IPAQ and administrative boundary accelerometer-captured vigorous-intensity physical activity (r = .43 [95% CI: .20 to .62]). Our findings suggest that the N-IPAQ provides good estimates of neighborhood-based physical activity and could be used when investigating neighborhood correlates of physical activity.