A model of a spatially homogenous stationary Cs-containing photoplasma far from optical saturation is developed for uniform spectral pumping within the D1 and D2 cesium line range. The plasma chemistry, radiation transfer, and ambipolar diffusion of charged particles are all explicitly considered. Unlike previous studies of sodium-containing photoplasmas, this work includes associative ionization at both resonance and non-resonance levels. Along with the penning and associative ionization processes, the first and second kind of electron collisions and stepwise ionization were considered. Radiation transfer is accounted for the Voigt profile for the resonance cesium lines in the Biberman-Holstein approximation, taking into account self-broadening and Van der Waals broadening of the lines by the buffer gas atoms. The electron density and temperature and densities of atomic and diatomic cesium ions were determined by solving a system of equations for the atomic level and ion densities as well as the electron energy balance. For example, parameters for pure Cs and Cs–Ar photoplasmas in a cylindrical cell were obtained over a wide range of resonance excitation rates and partial pressures of gas components. A comparison with previously obtained data for cesium and sodium photoplasmas was made. The results can be used to design photoelectric converters based on cesium-containing gas cells.