Self-assessment is a fundamental skill for professionals because self-assessment can promote self-regulated learning and professional development. However, studies reporting the use of self-assessment instruments in the professional training context are scarce. This study aimed to re-evaluate the psychometric properties of the Self-assessment Practice Scale (SaPS), which was originally developed in the school context, and extend its use to the professional training context. A sample of 200 investigative interviewer trainees from Australia and North America were invited to complete the modified SaPS. After removing misfitting items, the confirmatory factor analysis results confirmed a first-order four-factor solution. The multidimensional Rasch analysis demonstrated that the resultant 16 items had satisfactory fit to the Rasch model. In general, the results supported the use of the 16-item modified SaPS as a valid measure for the sample in this study. The potential of using the SaPS in professional training contexts is discussed.