Background: As a joint-preserving surgery, porous tantalum implantation (PTI) provides an additional treatment option for osteonecrosis of the femoral head (ONFH). However, conversion to a total hip arthroplasty (THA) after failed PTI is considered a challenging procedure. The purpose of this study was to compare the clinical and radiologic outcomes and complications of THA after failed PTI with those of primary THA without any previous surgery for ONFH. Methods: This retrospective study included 32 patients undergoing THA after failed PTI and 25 age, sex, and body mass index matched patients who underwent primary THA without any previous surgery for ONFH between December 2009 and March 2014. All patients were followed for at least 36 months. The postoperative clinical and radiological evaluations were based on Harris Hip Score (HHS) and plain radiographs. The independent sample test and the chi-square test were used for the statistical analysis. Results: The HHS in the PTI group was similar to that in the primary group at the latest follow-up (p = 0.274), but longer operation time and greater intraoperative blood loss were observed in the PTI group (p < 0.001, respectively). No significant differences in radiological parameters and postoperative complications were found between the 2 groups (p > 0.05). Conclusions: THA after PTI showed similar clinical and radiological outcomes to primary THA except for longer operation time and greater intraoperative blood loss.