Background The structural elements of the vascular wall, namely, extracellular matrix and smooth muscle cells ( SMC s), contribute to the overall stiffness of the vessel. In this study, we examined the crosslinking‐dependent and crosslinking‐independent roles of tissue transglutaminase ( TG 2) in vascular function and stiffness. Methods and Results SMC s were isolated from the aortae of TG 2−/− and wild‐type ( WT ) mice. Cell adhesion was examined by using electrical cell–substrate impedance sensing and PicoGreen assay. Cell motility was examined using a Boyden chamber assay. Cell proliferation was examined by electrical cell–substrate impedance sensing and EdU incorporation assays. Cell micromechanics were studied using magnetic torsion cytometry and spontaneous nanobead tracer motions. Aortic mechanics were examined by tensile testing. Vasoreactivity was studied by wire myography. SMC s from TG 2−/− mice had delayed adhesion, reduced motility, and accelerated de‐adhesion and proliferation rates compared with those from WT . TG 2−/− SMC s were stiffer and displayed fewer cytoskeletal remodeling events than WT . Collagen assembly was delayed in TG 2−/− SMC s and recovered with adenoviral transduction of TG 2. Aortic rings from TG 2−/− mice were less stiff than those from WT ; stiffness was partly recovered by incubation with guinea pig liver TG 2 independent of crosslinking function. TG 2−/− rings showed augmented response to phenylephrine‐mediated vasoconstriction when compared with WT . In human coronary arteries, vascular media and plaque, high abundance of fibronectin expression, and colocalization with TG 2 were observed. Conclusions TG 2 modulates vascular function/tone by altering SMC contractility independent of its crosslinking function and contributes to vascular stiffness by regulating SMC proliferation and matrix remodeling.