The phase behavior of aqueous mixtures of polymers and surfactants has been widely studied over the past thirty years. Not only for the academic interest in the richness in the structures formed, but also for the potential this combination holds in a number of different applications, ranging from cleaning products and cosmetics to pharmaceuticals and oil recovery. However, when developing these products, it is essential to know when the species are miscible, when the aim might be to build viscosity, or how to trigger associative phase separation, as for deposition of coacervates in care shampoos. The phase behavior is not only determined by the choice of the polymer and surfactant, but also to a large extent affected by additions of co-surfactants and salt, which will be discussed in this review. Additional aspects to be considered for less-studied, more natural and sustainable polymers and surfactants will also be presented.