Surgical treatment of hip dysplasia by arthroscopic procedures remains controversial. The aim of this study was to compare outcomes of periacetabular osteotomy (PAO) after failed hip arthroscopy to a matched-control group without previous arthroscopy. Fifty-two patients who underwent PAO after failed hip arthroscopy were matched to two subjects without arthroscopy based on age, sex, BMI and radiographic severity. Pre- and post-operative patient self-reported outcomes and radiographic parameters were compared at minimum 1-year follow-up. Prior to PAO the failed hip arthroscopy group exhibited lower modified Harris hip scores (mHHS; 57 versus 62; P = 0.04), WOMAC (59.9 versus 66.3; P = 0.08), UCLA activity (5 versus 7; P = 0.001) and SF12 physical scores (34 versus 40; P = 0.001) compared with the non-arthroscopy group. At minimum 1-year follow-up, the failed hip arthroscopy group had lower mHHS (78 versus 87; P = 0.003); worse WOMAC (84.1 versus 90.8; P = 0.02) and SF-12 physical component (46 versus 50; P = 0.02) with similar UCLA (7 versus 8; P = 0.21) compared with the non-arthroscopy group. No differences were detected regarding radiographic parameters or in patient-reported outcomes from preoperative to follow up. PAO achieved the desired radiographic correction and significant improvement in pain and function after a failed previous hip arthroscopy, however, the patient-reported outcomes were inferior to those of PAO without previous failed arthroscopy.