This paper presents the stiffness analysis of a planar 2DOF tensegrity mechanism. A stiffness model is first derived based on an existing formulation. Several stiffness indices having physical meaning are then extracted from the stiffness matrix for performance evaluation purposes. Stiffness mappings based on these stiffness indices are then plotted over the mechanism’s workspace and observations are made. It is shown, for instance, that in the case of the planar 2DOF tensegrity mechanism, the effect of the prestress on the stiffness is generally not significant when the stiffnesses of the cables and struts are assumed to be linear.