Climate change continues to undermine agricultural productivity and livelihoods in sub-Saharan Africa, where smallholder, rain-fed systems predominate. Kenya and Zimbabwe, representing contrasting decentralized and centralized adaptation systems, provide insights into how institutional design shapes agricultural resilience. This study conducts a comparative institutional analysis of climate change adaptation across four dimensions: land tenure, governance structures, access to inputs and resources, and community-based support. Using a systematic literature review (2000-2025), bibliometric mapping, and a Composite Institutional Adaptation Index (CIAI), the analysis examines how policies and local institutions interact to shape adaptive capacity. Findings indicate that Kenya's devolved governance facilitates local innovation through County Climate Change Funds, while Zimbabwe's centralized approach promotes policy coherence but constrains local autonomy. In both contexts, tenure security, equitable input access, and integration of cooperatives, traditional leaders, and women's groups emerge as critical determinants of resilience. The study situates these findings within debates on adaptation finance and governance, including Locally Led Adaptation, Green Climate Fund support, and CAADP implementation. It concludes that effective climate adaptation requires multi-scalar governance systems that integrate formal and informal institutions, align finance with local priorities, and embed learning within agricultural policy.