Cyclic guanosine monophosphate (cGMP) is an intracellular signalling molecule that acts as a second messenger in a wide range of cellular processes. In Dictyostelium cells, a unicellular organism, cGMP is known to regulate chemotaxis and cell migration. However, to date, cGMP activity in Dictyostelium has only been measured using biochemical assays, and visualisation of cGMP dynamics in live cells has not been possible. Now, Shigehiko Yumura and colleagues (Yumura et al., 2023) have adapted a mammalian fluorescent probe for cGMP, Green cGull, to enable cGMP visualisation in Dictyostelium cells. Here, they demonstrate that this modified reporter, D-green cGull, is sensitive enough to visualise propagating waves of cGMP within cells and thus measure changes in its dynamics. The authors use this to demonstrate that cGMP oscillations in aggregating Dictyostelium cells synchronise with oscillations in intracellular Ca2+ and cyclic adenosine monophosphate (cAMP). Furthermore, these waves precede propagation of actomyosin activity and cell migration during chemotaxis, and increases in intracellular cGMP induce relocalisation of myosin II from the cytosol to the cell cortex. Overall, this paper shows for the first time the spatiotemporal dynamics of cGMP in live Dictyostelium cells and presents novel insights into the function of cGMP in chemotaxis.