Purpose: To evaluate the correlation between PI-RADSv2.1 and International Society of Urologic Pathologists (ISUP) score for patients who underwent multiparametric-MRI(MpMRI) prior to transrectal ultrasound (TRUS) guided cognitive fusion biopsy (CF-Bx). And to investigate inter-observer agreement of PI-RADSv2.1. Methods: Patients who underwent MpMRI of prostate prior to first TRUS-guided CF-Bx, were included in this prospective study. MpMRI examinations were evaluated by two radiologists before biopsy according to the PI-RADSv2.1. Interobserver agreement was recorded and the final PI-RADS categorization was performed by consensus. Correlation of histopathological results with PI-RADSv2.1 score was evaluated. Lesions with Gleason Score(GS)≥6 were considered as prostate cancer (PCa). Results: A total of 84 patients with 106 lesions were included in the study. The ratio of PCa in the PI-RADS groups 1,2,3,4,5 was 0%, 0%, 22.2%, 56%, 94.45%, respectively. There was a positive correlation with a value of 0.814 between the PI-RADSv2.1 and the ISUP score. When PI-RADS≥3 is accepted as the cut-off value in peripheral zone(PZ) and the whole gland, the NPV for malignancy was 100.00%. For PI-RADS ≥4, it was 76.47% for PZ, and 80.65% for the whole gland. For the whole gland; sensitivity, specificity, and PPV of the PI-RADS≥3 were 100%, 12.9%, and 44.33%, respectively; for PI-RADS≥4, these values were 72.09%, 80.65%, and 72.09% respectively. Without applying cut-off values, the interobserver agreement for PI-RADS score was κappa:0.562. Conclusions: PI-RADSv2.1 was created in the framework of v2 to facilitate to evaluate MpMRI and to increase interobserver agreement. We believe that further studies will be necessary.