In African communities, informal associations are becoming increasingly important in shaping and mediating local adaptation practices. The study suggests that the concept of social innovation is useful for analyzing climate adaptation in the multiscale institutional environments with complex vulnerability contexts. Small-scale local associations have a potential to facilitate collective experimentation and risk management, contributing to the resilience and sustainability of the social-ecological system. Ethnographic focus is on the informal associations of economic cooperation and dispute mediation of Kuria people of northwest Tanzania, and the ways these institutional forms facilitate resource management and the negotiation of difference under income diversification. Organizational features of the groups are examined that facilitate social innovation and alternative patterns of communication, effecting flexible and relational connections between scales. The study examines the features of the local institutions that have a potential to enhance local adaptive capacity, and discusses possible challenges to sustainable climate adaptation.Highlights► Informal institutions in Africa affect local adaptive capacity to climate change. ► Kuria mutual help groups in Tanzania help improve climate resilience of the marginal. ► They facilitate resource management and dispute negotiation under ongoing income diversification. ► Social innovation is an important element in enhancing local adaptive capacity. ► Multiscale institutional involvement enables to address challenges to sustainable adaptation.