The understanding of the physical properties of hydrogels has been controversial because hydrogels inherently have a substantial amount of heterogeneities in their structures. In this study, we focused on one of the simplest heterogeneities, heterogeneous distribution of strand length, and investigated its influence on physical properties. We prepared Tetra-PEG gels with bimodal distribution in strand length (Tetra-PEG bimodal gels) by combining Tetra-PEG prepolymers with different molecular weights and measured the physical properties including elastic modulus and ultimate deformation ratio. The physical properties of Tetra-PEG bimodal gels were well described by the models for conventional Tetra-PEG gels with the average polymerization degrees between cross-links. We conclude that the mechanical properties of hydrogels that have heterogeneous distribution in strand length can be predicted from those of hydrogels with the average strand length in the range tested in this study.