Cell interactions with the extracellular matrix (ECM) are critical to cell and tissue functions involving adhesion, communication, and differentiation. Three-dimensional (3D) in vitro culture systems are an important approach to mimic in vivo cell–matrix interactions for mechanobiology studies and tissue engineering applications. This chapter describes the use of engineered microtissues as 3D constructs in combination with a magnetic tissue gauge (μTUG) system to analyze tissue mechanical properties. The μTUG system is composed of poly(dimethylsiloxane) (PDMS) microwells with vertical pillars in the wells. Self-assembled microtissues containing cells and ECM gel can form between the pillars, and generate mechanical forces that deform the pillars, which provides a readout of those forces. Herein, detailed procedures for microfabrication of the PDMS μTUG system, seeding and growth of cells with ECM gels in the microwells, and measurements of the mechanical properties of the resulting microtissues via magnetic actuation of magnetic sphere-tagged μTUGs are described.