Rotifers and cladocerans are important constituents and dominant groups of zooplankton communities. Interspecific competition between them is one of major driving forces regulating structure and function of aquatic ecosystem. It is generally believed that rotifers and large cladocerans are difficult to coexist, and rotifers are often excluded by large cladocerans, while rotifers and small cladocerans can coexist. In fact, the outcome of interspecific competition between rotifers and cladocerans was uncertain to a certain extent. In this review, we briefly introduced the patterns of competition between rotifers and cladocerans and their relative importance, and analyzed in detail the effects of environmental factors, including temperature, food resources, initial density, individual size, threshold food concentration, starvation tolerance ability, predation, allelopathic substances released by competitors and predators on the outcome of competition between rotifers and cladocerans. Finally, we put forward some scientific problems and research breakthrough points.