Collagen is the most abundant fibrous protein in the body’s extracellular matrix (ECM), traditionally assembled in hydrated environments under moderate crowding conditions that allow for proper cell proliferation. Achieving collagen assembly in highly crowded environments is paradoxical to conventional wisdom in that overpacked environments are not conducive to protein/peptide self-assembly. In this work, we employ poly(N-isopropylacrylamide) ultra-low crosslinked microgel (ULCs) pastes as a tunable, crowded environment within which collagen can be assembled. The combination of ULC pastes and collagen provides us with a new tool to control ECM mechanics, structure, and bio-integration. Indeed, ULCs are a particularly attractive colloidal building block owing to our synthetic control over their crosslinking, degradability, surface chemistry, and more. Here, we describe the development of composites of varying paste concentrations, visualize collagen assembly, and investigate mechanical properties. By successfully integrating these components, we provide methods to develop dense collagen-based materials with controllable properties.