Background The Modifiable Activity Questionnaire (MAQ) is a physical activity questionnaire shown to be both valid and reliable in French. After translation and adaptation to Dutch, the objective of the study was to see whether this questionnaire was valid and reliable in the Dutch language and thus could be used as a tool for the detection of exercise levels in a Dutch native-speaking population. Methods After translating and back translating the valid French version of the MAQ into Dutch, the final product of the Dutch version was tested twice in the same population (n = 101) interrupted by 1 week for the assessment of the test–retest reliability. To measure concurrent validity, the valid Dutch version of the IPAQ was filled in at the same time as the MAQ. To measure the construct validity of this assessment tool, a smaller sample size (n = 28) of the total population carried an accelerometer for 1 week. Results The intraclass correlation coefficient for the test– retest reliability was 0.78 (p \ 0.01), suggesting a good test–retest reliability. Pearson’s rho correlation coefficient between the IPAQ and the MAQ was 0.41 (p \ 0.01), suggesting a medium concurrent validity. Pearson corre- lation statistics showed a low, non-significant correlation coefficient (r = 0.243, p = 0.213) when measuring con- struct validity. Conclusion The present study shows that the Dutch lan- guage of the MAQ is reliable and has a medium concurrent validity. Although the construct validity is low, these results are in line with previous validation studies of physical activity questionnaires.