Purpose: To find how effective is preoperative hip aspiration for detecting infections in patients slated for conversion THA. Methodology: This retrospective study evaluated patients who were scheduled for conversion THA following failed ORIF. All participants underwent preoperative ESR/CRP testing, joint aspiration, and intraoperative cultures, with the latter serving as the diagnostic gold standard. Results: The sensitivity of preoperative hip aspiration was 17.7%, although specificity was high at 81.0%. For CRP, an area under the curve (AUC) of 0.643 was observed, and a cutoff value of 8.8 mg/L exhibited a sensitivity of 64.3% and specificity of 64.7%. ESR did not show promise as a diagnostic tool, with an AUC of 0.577. Conclusions: Preoperative hip aspiration exhibited poor sensitivity, though high specificity, for diagnosing infections in patients undergoing conversion THA. CRP values demonstrated moderate diagnostic potential, while ESR did not show significant promise.