The benefits of process-oriented group supervision are difficult to evaluate, as the validity and reliability of the existing instruments have been questioned. The aim was to develop and test the psychometric properties of a questionnaire in order to evaluate the effects of process-oriented group supervision on nursing students during their three-year nursing education. A 55-item Process-oriented Group Supervision Questionnaire (PGSQ) with a developmental design was formulated on the basis of a literature review and the expectations of nursing students who participated in a three-year nursing education programme (N = 176). Construct validity and internal consistency reliability were tested at the end of each study year: year 1 (T1), year 2 (T2), and year 3 (T3) by means of exploratory factor analysis and Cronbach’s coefficient. An adequate explorative factor analysis (principal component analysis, varimax rotation) with an Eigenvalue >1.0 and factor loadings >0.40, reduced the questionnaire to 18 items comprising three factors labelled educative, supportive and developmental, which explained 60.2% at T1, 71.8% at T2, and 69.3% at T3 of the total cumulative variance. The corresponding Cronbach’s coefficient figures were 0.89 (T1), 0.94 (T2) and 0.93 (T3). The 18-item PGSQ is considered to be a short and useful tool due to its satisfactory validity and reliability figures.