Dinoflagellates are unicellular algae that can have photosynthetic or nonphotosynthetic lifestyles. Dinoflagellates in the genus Symbiodinium can enter endosymbiotic associations with corals, providing the metabolic basis for the highly productive and biologically diverse coral-reef ecosystems (Hoegh-Guldberg, 1999), as well as with other cnidarians, including sea anemones and jellyfish, and noncnidarian hosts (Trench, 1993; Lobban et al., 2002; Mordret et al., 2016). Here I describe a protocol for isolating totalDNA from Symbiodinium cells.