Kenya’s devolved climate governance architecture positions county governments as the operational sphere for translating climate and gender commitments into gender-responsive climate action. Yet a persistent gap remains between formal policy and substantive equity outcomes. This article asks why decentralised governance structures shape gender-responsive as a governance principle to produce equitable outcomes of climate interventions in Busia County, Kenya. A convergent parallel mixed-methods design integrated data from, 435 survey respondents across seven sub-counties, eight key informant interviews, four focus group discussions and documentary analysis of 14 policy instruments. Two regression models examined the institutional determinants of gender mainstreaming and gender-equitable climate outcomes. Institutional capacity was the strongest determinant of gender mainstreaming (β = 0.570), exceeding the influence of socio-cultural factors (β = 0.244), with the model explaining 57.2% of the variation. Implementation strategy exerted a stronger influence on gender-equitable outcomes (β = 0.403) than resource access (β = 0.267), with the model explaining 44.3% of the variation. Qualitative and documentary evidence identified four interrelated mechanisms mediating these relationships: weak fiscal and monitoring instrumentation, access to resources without corresponding control, procedural inclusion without substantive influence, and reliance on civil society for accountability. The article argues that decentralization in Kenya has achieved negative subsidiarity, without positive subsidiarity: that devolution has enabled the downward transfer of climate governance functions without consistently transferring the institutional capacity, fiscal instruments, authority, and accountability necessary to make gender responsiveness durable and effective. Its central contribution is to demonstrate that institutionalizing gender responsiveness requires moving beyond formal inclusion towards implementation systems capable of converting policy commitments into decision-making power, equitable resource access, and demonstrable protection from gendered climate vulnerability.