Objectives: The aim of this study was to adapt the World Health Organization’s (WHO) Global Physical Activity Questionnaire (GPAQ) into Turkish and evaluate its reliability and validity among Bornova Municipality employees. Patients and methods: The questionnaire was given its final Turkish form after its translation by two independent translators, a consensus meeting with both translators and the revision of the back-translation. An expert panel was organized for face validity and expert opinions were collected for content validity. The data of the study were collected in Municipality of Bornova district, Izmir province of Turkey between August 2016 and November 2016. Test-retest was used for reliability, International Physical Activity Questionnaire (IPAQ) was used for concurrent validity, and a pedometer was used for criterion validity. Among a total of 2,137 workers, a sample size of 352 employees was determined using 33% prevalence with 5% error margin, 95% confidence interval, and 20% non-response rate. The participants were selected with systematic sampling and 287 (81.5%) workers (183 males, 104 females; mean age: 38.9±8.5 years; range, 22 to 63 years) participated in the study. Results: Reliability coefficients were substantial, near perfect (Kappa 0.74-0.87, p<0.001; Spearman rho 0.77-0.91, p<0.001). A substantial, near perfect relationship was found between IPAQ and GPAQ (r=0.79-0.94, p<0.001). For criterion validity, a fair relationship was found between the pedometer results and GPAQ (r=0.32, p=0.001). As for discriminant validity, the participants with physically active jobs had higher levels of physical activity compared to others (median: 3,240, 960 metabolic equivalent [MET]-min/per week, p<0.001). Those with an income below the poverty line had median 2,400 MET-min/week compared to 1,200 for participants above the poverty line (p<0.001). A significant difference was found among different education duration of employment groups. Conclusion: The Turkish version of GPAQ is reliable and valid. Further validity and reliability studies of the GPAQ among non-working groups such as housewives, students, and unemployed ones can be recommended. Based on these findings, the GPAQ can be used as a valid and reliable tool in the Turkish population.