What model of agricultural transformation can reach the policy goals of just transformation and increased productivity in thediverse African smallholder sector? A response to this question relies on studies that examine outcomes of local agriculturalinvestments. A significant, yet under-studied, example of these investments is small-scale public investments in irrigation. Toaddress this gap, we analyse social differentiation and accumulation patterns arising from donor-supported public investmentsin irrigation in four villages in the Kilombero District, Tanzania. Participatory wealth ranking and interviews reveal that invest-ments in small-scale smallholder irrigation fuelled a process of accumulation from ‘below’. We discuss how these investmentscan be considered more inclusive than ‘from above’ accumulation (from extra-local investments), while nonetheless contributingto some differentiation among smallholders. We conclude that public investments that align with smallholders' initiatives in irri-gation development are more likely to contribute to policy goals of socially inclusive improved agricultural productivity.