Extracellular matrix incorporated within a scaffold plays an important role in assisting cell behavior in neural tissue engineering. In this study, we investigated how the concentration of fibronectin (FN) affected neurite growth when incorporated within a synthetic polymer gel made of poly(ethylene glycol) (PEG) or a natural polymer gel of collagen I. Mechanical and chemical properties of the scaffold were varied by using a range of concentrations of gels and FN. Rheology was used to determine the mechanical stiffness of hydrogels and neurite length and viability were measured to evaluate cell response. In both types of gels, increasing the concentration of the base scaffold (PEG or collagen) increased the mechanical stiffness as denoted by G∗. Neurite lengths in PEG gels increased with increasing FN concentration and decreased with increasing G∗. In collagen gels, FN reduced neurite extension for the lowest concentrations of collagen (0.4-0.6 mg/mL) while FN increased neurite extension for mid and high collagen concentrations (1.0-2.0 mg/mL). The results from these two different scaffolds indicate that both stiffness and FN concentration impact the growth of the neurite and that the addition of small amounts of FN (100 μg/ml) permits PEG gels to perform on par with similar stiffness collagen gels.