This study aimed to translate the Pregnancy Physical Activity Questionnaire (PPAQ) into Vietnamese, and test its reliability and validity among Vietnamese pregnant women. Intraclass correlation (ICC) and the Bland and Altman method were used to assess the test-retest reliability of the PPAQ. The Pearson correlations coefficient between the PPAQ measurements and those obtained from a pedometer that measured step counts (10-day averages) were used to determine the validity of the questionnaire. The PPAQ was successfully translated from English into Vietnamese with face validity through a rigorous process of the cross-cultural validation. For the analysis of reliability, the ICC value was 0.88 (95% CI 0.83-0.94) for total activity, 0.94 for sedentary, 0.88 for light, 0.90 for moderate, and 0.87 for vigorous activities. The Bland and Altman analysis showed that the first and second PPAQ total scores did not significantly differ from zero, and mostly fell within the range of 0 +/- 1.96 SD. The analysis of validity showed that there were moderate correlations with statistically significance (p = 0.02) between the step counts and PPAQ total. Our study indicates that the Vietnamese PPAQ is within acceptable reliability and validity.