This study aimed to develop a suitable hydrogel-based 3D platform to support long-term culture of primary endothelial cells (ECs) and fibroblasts. Two hydrogel systems based on allyl-modified gelatin (gelAGE), G1MM and G2LH, were cross-linked via thiol-ene click reaction with a four-arm thiolated polyethylene glycol (PEG-4-SH). Compared to G1MM, the G2LH hydrogel was characterized by the lower polymer content and cross-linking density with a softer matrix and homogeneous and open porosity. Cell viability in both hydrogels was comparable, although the G2LH-based platform supported better F-actin organization, cell-cell interactions, and collagen and fibronectin production. In co-cultures, early morphogenesis leading to tubular-like structures was observed within 2 weeks. Migration of fibroblasts out of spheroids embedded in the G2LH hydrogels started after 5 days of incubation. Taken together, the results demonstrated that the G2LH hydrogel fulfilled the demands of both ECs and fibroblasts to enable long-term culture and matrix remodeling.