Introduction: The short International Physical Activity Questionnaire (IPAQ-short) has frequently been used for national and international comparable physical activity (PA) prevalence studies. The purpose of this paper is to describe a Greek version of IPAQ-short (IPAQ-Gr) and present its reliability properties in Greek young and healthy adults. Methods: Two hundred and eighteen health science students of the Athens Technological Educational Institute, aged 19-29 years, were randomly selected and participated in the study. An intra-examiner reliability study over time (8 and 30 days apart) was carried out to assess IPAQ-Gr repeatability. An inter-examiner reliability study was also performed to assess the consistency of IPAQ-Gr outcomes between examiners. At the same time, an intra-examiner reliability study using an independent sample of 175 medical students at the University of Ioannina was carried out in order to examine multi-centre IPAQ-Gr reliability. Intra-class correlation coefficients for IPAQ scores and kappa statistics and percent agreement for physical activity classification were used in the analysis. Results: Intra-class correlation coefficients (ICCs) between day-1 and day-9 assessments for IPAQ total and vigorous PA were high in all groups examined (0.84 to 0.93). ICCs for walking PA, moderate PA and sitting hours were lower, but still good (0.69 to 0.81). Repeatability of IPAQ-Gr outcomes after one-month re-administration was high for total and vigorous PA (0.87, 0.81) and good for moderate (0.66) and walking PA (0.75). Inter-examiner reliability data showed that all correlations between examiners were greater than 0.70, up to 0.87 (paired t-test, p=NS), with the exception of moderate PA, where correlations were weaker (0.58 to 0.64). Similar results were found when intra-examiner correlations were compared between educational institutes (multi-centre inter-examiner reliability of IPAQ). Conclusions: IPAQ-Gr was found to present acceptable reliability properties in Greek young adults. IPAQ-Gr showed high repeatability values for total and vigorous PA, and good for moderate and walking PA.