Self-assembled multilayer thin films formed by the sequential adsorption of polyelectrolytes from aqueous solution were used as nanoreactors for the in situ growth of silver nanoparticles. Carboxylic acid groups within poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) multilayer films or PAA and poly(ethyleneimine) (PEI) multilayer films bind silver cations by ion exchange with acid protons. PEI is also appealing because its structure contains amine groups which can form metal ion complexes. Silver ion containing multilayer films can be subsequently chemically or photochemically reduced to yield polymer/silver nanoparticle composites. The number of available carboxylic acid groups capable of binding silver cations within multilayer films is strongly dependent on the processing conditions of the multilayer assembly. A combination of UV-visible spectroscopy and transmission electron microscopy shows that nanoparticle size and concentration can be controlled through the assembly pH of PAH/PAA and PEI/PAA films. Furthermore, using these techniques we also take a closer look at the silver ion exchange process. Because free carboxylic acid groups bind metal ions upon immersion of the thin film in a metal salt solution, the effects of silver ion concentration in solution and exchange time on nanoparticle formation are explored in multicombinatorial experiments.