This study examines how domestic political consolidation shapes foreign policy autonomy in emerging democracies, using a comparative analysis of Nigeria and South Africa during the 2023–2025 period. While both countries possess substantial material capabilities and long-standing regional leadership roles, they experienced marked constraints on their foreign policy autonomy amid electoral transitions, economic pressures, security challenges, and shifting geopolitical alignments. Drawing on neoclassical realism and two-level game theory, the study adopts a qualitative, conceptual research design based on systematic secondary data analysis to trace the domestic mechanisms through which consolidation deficits translate into constrained international agency. The findings demonstrate that foreign policy autonomy is not determined by material power alone but is critically mediated by domestic political legitimacy, institutional capacity, economic stability, security conditions, and elite consensus. In both cases, legitimacy crises undermined diplomatic credibility, economic vulnerabilities narrowed strategic options, security preoccupations diverted resources inward, and domestic veto players constrained executive flexibility in international negotiations. The study further reveals that the relationship between consolidation and autonomy is non-linear and dynamic, with feedback effects whereby foreign policy failures exacerbate domestic political weaknesses, creating reinforcing cycles of constraint. Comparatively, the analysis identifies convergent patterns of constrained regional leadership alongside divergent dynamics rooted in institutional quality, coalition politics, alliance preferences, and regional organizational contexts. These findings refine neoclassical realist theory by foregrounding political legitimacy as a critical yet under-theorized intervening variable linking domestic politics to foreign policy outcomes, and by demonstrating multiple causal pathways through which consolidation deficits limit international agency. The study concludes that sustained foreign policy autonomy in emerging democracies depends fundamentally on domestic political consolidation. By integrating insights from international relations and comparative democratization scholarship, the article contributes to broader debates on power, autonomy, and leadership in the Global South, with policy-relevant implications for democratic consolidation, regional governance, and international partnership strategies.