Background To determine the utility of diagnostic 18F-DCPyL PSMA-PET/CT to aid management of men with highly suspicious multiparametric MRI prostate (PIRAD 4–5 lesions) and discrepant negative prostate biopsy. Methods A multicentre prospective consecutive case series was conducted (2018–2021), recruiting men with prior mpMRI prostate PIRADS 4–5 lesions and negative prostate biopsy. All men had 18F-DCPyL PSMA-PET/CT with subsequent management based on the concordance between MRI and PET: (1) Concordant lesions were biopsied using in-bore MRI targeting; (2) PSMA-PET/CT avidity without MRI correlate were biopsied using cognitive/software targeting with ultrasound guidance and (3) Patients with negative PET/CT were returned to standard of care follow-up. Results 29 patients were recruited with 48% ( n  = 14) having concordant MRI/PET abnormalities. MRI targeted biopsy found prostate cancer in six patients, with grade groups GG3 ( n  = 1), GG2 ( n  = 1), GG1 ( n  = 4) found. Of the 20 men who PSMA-PET/CT avidity and biopsy, analysis showed higher SUVmax (20.1 vs 6.8, p  = 0.036) predicted prostate cancer. Of patients who had PSMA-PET avidity without MRI correlate, and those with no PSMA-PET avidity, only one patient was subsequently found to have prostate cancer (GG1). The study is limited by small size and short follow-up of 17 months (IQR 12.5–29.9). Conclusions PSMA-PET/CT is useful in this group of men but requires further investigation. Avidity (higher SUVmax) that correlates to the mpMRI prostate lesion should be considered for targeted biopsy.