<p>This study examined the impact of privatization on technical efficiency in Nigerian manufacturing using a two-stage data envelopment analysis and regression framework. Ten fully privatized firms were analyzed over 5 years before (2013–2018) and after privatization (2019–2023). In the first stage, DEA generated efficiency scores for output and profit. In the second stage, these scores were regressed against firm size, age, and concentration ratio using random effects with GMM robustness checks. The findings reveal a complex picture. Output efficiency improved after privatization, with seven firms on the frontier in both periods though notably, different sets of firms achieved this status, indicating significant re-ranking. Profit efficiency tells a different story: average profits declined, and the number of profit-efficient firms fell from six to four. Regression results show that firm size positively predicts output efficiency but negatively predicts profit efficiency, suggesting larger firms achieved scale economies while carrying legacy costs that eroded profitability. Firm age consistently predicts profit efficiency, revealing that organizational experience became a valuable intangible asset in competitive markets. The study concludes that privatization outcomes are contingent on firm-specific characteristics particularly size and age. Success depends not on ownership change alone but on aligning firm characteristics with market structure and institutional support.</p>