In this research, variations of tensile properties and fracture behavior of 316L austenitic stainless steel weld metal as a function of aging temperature and time have been investigated. Stainless steel plates were butt-welded using GTAW process. Weld metal tensile specimens were subjected to various aging heat treatments at temperatures of 750 and 850°C for periods of 1 to 100 hours prior to tensile tests at 25 and 500°C. Dissolution of delta-ferrite and formation of sigma phase network during aging resulted in a mild increase in tensile strength and significant reduction in ductility, particularly at 25°C. Although fracture surfaces exhibited ductile features, the dimple morphology and the macroscopic fracture mode were found to be affected by aging. The unaged weld metal exhibited a classic mode of cup and cone fracture, whereas slant and flat types of fracture modes were observed in the aged weld metals, with the slant mode being dominant at 500°C. The slant mode was associated with deformation localization along arrays of primary voids, nucleated at cracked sigma phase particles, oriented at about 45° to loading direction. The transition in the fracture mode is further discussed based on variations in the dimple morphologies and strain hardening exponent.