This major research paper applies a critical discourse analysis (CDA) to examine the Ontario government’s rationalization of full day kindergarten to the public and the underlying discursive representation of social citizenship that the government sets forth. A content analysis of nineteen textual documents identified twelve rationales for FDK. A social investment discourse was identified as the dominant discourse underlying these rationales, while a social justice discourse and a combination of both discourses was also present. A CDA of three textual documents indicated that the Ontario government employed nominalization, modality and interdiscursivity to perpetuate the social investment discursive representation of FDK. The prevalence of social investment discourse in the Ontario government’s rationalization of FDK holds important implications for advancing just and caring early childhood policy for all children and families.