Cell contraction force plays an important role in wound healing, inflammation, angiogenesis and metastasis. Among techniques that allow to evaluate cell contraction or traction force, we found the collagen contraction assay. This method, firstly described as fibroblast-populated collagen lattice, has been widely used with mainly cell types whose principle relies on the force generated by cells within the gel that interact with collagen lattice. Most of the studies aiming to evaluate the traction force generated by cells only rely on imaging and measuring the gel area from a top view during a defined time after the induction of the gel contraction. In addition, although the versatility and efficiency of the collagen gel contraction assay has been demonstrated, it does not provide any quantification of cellular traction force as mechanical properties and more precisely gel stiffness is not evaluated in this method. Therefore, to better evaluate the cell traction force, we implemented a mechanical dimension by evaluating collagen gel stiffness by atomic force microscopy. This study demonstrates that TGF-beta treated collagen-embedded cells can induce a significant increase in fibroblast traction force by measuring the Young’s modulus of the gel. The collagen matrix used in this three-dimensional model provide close conditions to a physiological environment for fibroblasts. Hence, in addition to evaluate cell traction force in response to a stimulation, this approach also allows to analyse production of proteins by fibroblast such as extracellular matrix proteins. To go further, this assay also allows to analyse fibroblast behaviour to external stress such as UV or blue light exposure. Overall, this method correlated to mechanical properties of the collagen gels may provide applications for the development of active ingredient involved in the well-aging including compounds with wound healing or anti-wrinkling potential.