Self-assembling peptides are attractive materials for tissue engineering applications because of their functionality including high biocompatibility and biodegradability. Modification of self-assembling peptides with functional motifs, such as the cell-adhesive tripeptide sequence RGD leads to functional artificial extracellular matrices (ECMs). In this study, we developed an artificial self-assembling ECM protein tethered with a growth factor via heterotrimer triple-helix (helix A/B/C) formation. The helix A and helix C peptides, which are capable of forming a heterodimer coiled-coil structure, were fused to both ends of a matrix protein composed of the elastin-derived structural unit (APGVGV)12 with an RGD motif. The helix B peptide, which constituents the third helix of the triple-helix structure, was fused with basic fibroblast growth factor (bFGF) for tethering to the artificial ECM proteins. Each recombinant protein exhibited cell adhesion and cell proliferation activities similar to the original, while the designed bFGF-tethered ECM protein exhibited superior cell proliferation activity. These results demonstrate that the approach of creating growth factor-tethered self-assembling proteins via triple-helix formation can be applied to develop functional ECMs for tissue engineering applications.