This article evaluates the evolution of civilian control over the armed forces in Bulgaria across two decades of North Atlantic Treaty Organization (NATO) membership (April 2004 — April 2024), combining a longitudinal institutional analysis with a structured regional comparison. The study develops an original composite indicator, the Civilian Oversight Completeness Index (COCI), which aggregates seven dimensions of civil control — parliamentary oversight, executive–ministerial balance, judicial autonomy over military justice, intelligence oversight, defencebudget transparency, media and civil-society engagement, and procurement transparency — each scored on a 0-to-10 scale using coded indicators drawn from NATO host-nation assessments, DCAF peer reviews, Transparency International Defence Index data, V-Dem and Varieties-ofDemocracy micro-variables, Bulgarian National Audit Office reports, and a systematic reading of 124 parliamentary-committee transcripts. The empirical analysis yields three principal findings. First, Bulgaria's aggregate COCI score rose from 4.2 (2004) to 7.3 (2024), a gain of 3.1 points that places Bulgaria in the upper-middle tier of Central and Eastern European NATO members but clearly below Slovenia (8.1), Slovakia (7.6) and Romania (7.4). Second, the institutional progress is highly uneven across dimensions: parliamentary formal powers, executive civilianisation, and budget transparency advanced by more than 3.5 points each, whereas judicial autonomy over military justice, intelligence oversight, and procurement transparency improved by only 1.6, 1.1 and 1.4 points respectively, producing a pronounced dimensional-disparity index of 0.47. Third, the gap between formal and substantive civil control in Bulgaria — captured by the COCI versus the Bertelsmann Transformation Index (BTI) substantive-democracy score — stands at 1.2 points in 2024, compared with 0.4 in Slovenia, 0.5 in Slovakia, and 0.8 in Romania, indicating the largest institutional-substantive gap in the regional peer group. The article interprets these findings through a political-institutionalist lens and argues that Bulgaria exemplifies a trajectory of accelerated formal compliance combined with retarded substantive democratisation, in which NATO accession pressure consolidated formal oversight architecture but left three residual deficits — parliamentary depth, intelligence autonomy, and procurement transparency — only partially addressed. The article concludes with policy implications for NATO enlargement conditionality, for the Allied Centres of Excellence agenda on resilient governance, and for the prospective security-sector-reform trajectories of non-member Western Balkan states