The coordination of metabolism with cell growth is critical for regulation of organismal development. Therefore there is significant interplay between metabolic enzymes and key developmental regulators such as transcription factors. The enzyme CTP synthase (CTPsyn) is essential for metabolic homeostasis as well as growth and development, due to its role in synthesising precursors for many fundamental cellular macromolecules such as RNA and lipids. However, the mechanisms by which CTPsyn is regulated during development are little understood. Here we have shown that Myc, an oncogene and a key development regulator, is necessary and sufficient for the assembly of CTPsyn-containing macrostructures termed cytoophidia. We show that the presence of CTPsyn is required for Myc to mediate its effect on cell growth during Drosophila development. Roles for CTPsyn and Myc in tumourigenesis have been well established and both proteins have been considered promising therapeutic targets. By better understanding the relationship between these two proteins, we can gain important insights, not only into tumour pathology and aetiology, but also metazoan developmental processes.