Background Comprehensive Geriatric Assessment (CGA) is decisive in patient-centered medicine of the aged individual, yet it is not systematically used. Aim The aim of this study was to provide precise practice-relevant time expenditure data for the Multidimensional Prognostic Index (MPI), a questionnaire-based frailty assessment tool. Methods MPI was determined in ninety older multimorbid adults in three geriatric departments (cohorts 1, 2 and 3). The time needed to perform the MPI (tnpMPI) was recorded in minutes. Follow-up data were collected after 6 months. Results The median tnpMPI was 15.0 min (IQR 7.0) in the total collective. In the last visited cohort 3, the median was 10.0 min and differed significantly from cohorts 1 and 2 with medians of 15.5 and 15.0 (p < 0.001). Conclusion These findings indicate, that MPI, as a highly informative frailty tool of individualized medicine, can be performed in an adequately practicable time frame.