Biomechanical properties are important for living tissues and cells. They are indicators of functional changes and pathological variations in the micro-structure, such as during tumor development. The topic of this thesis falls at the intersection of biomechanics and optical imaging, and focuses on optical elastography, an optical sensing and imaging technique used to measure biomechanical properties at the tissue and cell levels. Optical coherence elastography, multiphoton elastography, and magnetomotive microscopy are developed, demonstrated, optimized, and applied at the tissue level to ex vivo breast cancer and in vivo skin, and at the cellular level to mouse macrophages in culture. Driven by scientific needs to engineer new quantitative methods that utilize the high micro-scale resolution achievable with optics, results of biomechanical properties were obtained from the biological samples. The results suggest potential diagnostic and therapeutic clinical applications. Results from these studies also help our understanding of the relationship between biomechanical variations and tissue/cell functional changes in biological systems. Therefore, the engineering of imaging techniques is employed to investigate biomechanics, as well as the feasibility for using these techniques to solve more scientific and clinical questions.