Gestational diabetes mellitus (GDM) is a common complication during pregnancy. Evaluation of the quantitative physical activity in diabetic pregnant women is critical. The aim of this study was to test the reliability and validity of the Pregnancy Physical Activity Questionnaire (PPAQ) in Turkish patients with GDM. A total of 120 pregnant women between the ages of 18 and 44 years with GDM were included. The reliability of the questionnaire was measured by internal consistency and analysis of 2-week test-retest reliability. Of the patients, 74 completed the test-retest procedure. Concurrent validity was examined by comparing the PPAQ with the Short Form of the International Physical Activity Questionnaire (IPAQ) in 36 patients. Test-retest intraclass correlation coefficient scores varied between 0.72 and 0.95. The Spearman rank correlation analysis showed that the PPAQ total activity values were statistically significantly correlated with the total values of IPAQ-Short Form ( = 0.410 and  = .030). In conclusion, the Turkish version of the PPAQ is a valid and reliable tool for the measurement of the physical activity level of pregnant women with GDM. Impact statement The pregnancy physical activity questionnaire (PPAQ) developed in 2004 by Chasan-Taber et al.; is a simple and short questionnaire measuring the frequency, duration, and intensity of physical activity in pregnant women. To date, this questionnaire has been translated into many languages and has been used in a number of studies. The aim of this study was to test the reliability and validity of the PPAQ in Turkish pregnant women with GDM. On the basis of our study results, we suggest that the Turkish version of the PPAQ is a valid and reliable tool for the measurement of the physical activity level of pregnant women with GDM. Evaluation of the quantitative physical activity in diabetic pregnant women may contribute to gain a better understanding of the role of physical activity during treatment and may be useful to compare the results of different studies carried out in different places more effectively.