The phase behavior of particle-polyelectrolyte complexes was systematically studied using a model system comprising oppositely charged silica nanoparticles and poly(allylamine) hydrochloride (PAH) polycations. Phase behaviors of aqueous mixtures of silica nanoparticles and PAH were elucidated over a wide parameter space of particle and polyelectrolyte concentrations as well as solution pH. Trends in phase behaviors were analyzed to create a fundamental understanding of the fundamental properties that govern the complexation of these oppositely charged species.