Effective and progressive civil society movements are critical for tackling poverty and protecting the environment in low-income countries. Strengthening the capacity of citizens and advocacy organisations can therefore be a meaningful contribution to local, national and international efforts to shape development sector policy. But agency is rarely talked about in relation to capacity strengthening. The definition of capacity strengthening used in advocacy programmes tends to focus on strengthening skills and knowledge, whereas agency is about fostering independent action and free choices. In this paper highlight lessons and insights from Sustainable Diets for All (SD4All), an advocacy programme that focuses on capacity strengthening and agency in its aim to foster change within local and national food systems. Spanning Bolivia, Indonesia, Kenya, Uganda and Zambia, experiences from SD4All highlight the dilemmas and tensions that Northern funders and Southern CSOs face when seeking common cause in advocacy agendas – particularly when the changes sought should be grounded in citizen agency.