Climate change is an existential threat to small island developing states. Policy coherence aims to create synergies and avoid conflicts between policies. Mainstreaming adaptation across multiple sectors and achieving greater coherence amongst policies is needed. The paper applies qualitative document analysis, content analysis, and expert interviews to examine the degree of coherence between climate-sensitive sector policies in framing climate change adaptation and the adaptation goals outlined in the national development plan and national climate change policies in St. Vincent and the Grenadines (SVG), Grenada, and Saint Lucia. The results indicate that adaptation is not fully integrated into the water, agriculture, coastal zone, and forestry policies. For example, while adaptation was explicitly addressed in Saint Lucia’s water policy, it was not explicitly addressed in SVG’s and Grenada’s water policy. The results show that Saint Lucia has the highest coherence score (93.52) while St. Vincent and the Grenadines has the lowest (91.12). The optimal coherence score that can be possibly obtained is 147, which indicates partial coherence in adaptation mainstreaming in sectoral policies. Expert interviews highlighted problems such as institutional arrangements, a silo approach, funding mechanisms, and policy implementation. Using the knowledge provided by the experts, a seven-step process is proposed to practically achieve policy coherence and operationalize the policies.