Adipose tissue (AT) expansion in obesity is characterized by cellular growth and continuous extracellular matrix (ECM) remodeling, with increased fibrillar collagen deposition. It is hypothesized that the matrix can inhibit cellular expansion and lipid storage. It is therefore important to fully characterize the ECM's biomechanical properties and its interactions with cells. In this study we characterize and compare the mechanical properties of human subcutaneous and omental tissues, which have different physiological functions. AT was obtained from 44 subjects undergoing surgery. Force-extension and stress-relaxation data were obtained. The effects of osmotic challenge were measured to investigate the cellular contribution to tissue mechanics. Tissue structure and its response to tensile strain was determined using nonlinear microscopy. AT showed non-linear stress-strain characteristics up to 30% strain. Comparing paired subcutaneous and omental samples (n=19) the moduli were lower in subcutaneous: initial 1.6±0.8KPa (mean±SD) and 2.9±1.5KPa (p=0.001), final 11.7±6.4KPa and 32±15.6KPa (p<0.001) respectively. The energy dissipation density was lower in subcutaneous AT (n=13): 0.1±0.1KPa and 0.3±0.2KPa respectively (p=0.006). Stress-relaxation followed a two-exponential time course. When the incubation medium was exchanged for deionized water in specimens held at 30% strain, force decreased by 31% and the final modulus significantly increased. Nonlinear microscopy revealed collagen and elastin networks in close proximity to adipocytes and a larger-scale network of larger fiber bundles. There was considerable micro-scale heterogeneity in the response to strain in both cells and matrix fibers. These results suggest that subcutaneous AT has greater capacity for expansion and recovery from mechanical deformation than omental AT.