The present study was designed basically to develop a psycho-motor mechanism scale based on the theory of translation competence proposed by PACTE (2003), and then to assess the validity and reliability of the constructed scale. In this quantitative research, after designing the scale, two translation tasks were given to 90 M.A. students majoring in translation studies at four different branches of Islamic Azad University. Based on the ratings by two experienced raters, the reliability and validity of the scale were determined. Therefore, two types of validity including concurrent and construct validity were assessed. The possible correlation between TOEFL PBT, as the test of linguistic ability and the researcher constructed psycho-motor scale was later checked, and verified. Next, the possible correlation between holistic scale for translation quality assessment developed by Waddington (2001), and the researcher constructed psycho-motor scale was examined and proved. For calculating the construct validity of the scale, factor analysis was run to probe the underlying constructs of the eight components of the researcher-constructed psycho-motor mechanism scale. As for reliability, the correlation between the two ratings by the raters based on the constructed scale was calculated and the scale was found to be reliable. The present findings, approved by the validity and reliability of the researcher-constructed scale, can contribute to the field of translation studies, which seems to be in great need of objective and communicative scales for translation tasks based on an anchored and consolidated theory of translation quality assessment like that of PACTE (2003).