This chapter reviews the current knowledge on “mixotrophy” among freshwater and marine dinoflagellates. The term “mixotrophy” is here used for the combination of phototrophy and phagotrophy in the same organism. Among the dinoflagellates it includes species with their own permanent chloroplasts (called constitutive mixotrophs, CMs) and species which lack their own chloroplasts and instead sequester chloroplasts from their prey (called non-constitutive mixotrophs, NCMs). We document here that mixotrophy is widespread among dinoflagellates with species representatives of both groups. Feeding may not always be expressed among the CM dinoflagellates, especially as light and nutrients impact feeding for the majority of dinoflagellates. Mixotrophic dinoflagellates primarily eat other protists, but some species can exploit large prey and metazoans as part of their diet. Some mixotrophic dinoflagellates are highly selective in which prey types they ingest, while others are quite omnivorous. Especially the NCM dinoflagellates seem to be quite restricted in which types of prey they can utilize as donors of chloroplasts and other cell organelles. Few data are available on in situ grazing rates of mixotrophic dinoflagellates, and there is a strong need to develop new techniques to measure in situ grazing rates. Development of reliable in situ techniques to measure feeding is not only important to assess the significance of phagotrophy as a way for dinoflagellates to harvest nutrients in inorganic nutrient limited waters, but also to assess the impact dinoflagellate mixotrophy on the food web