We studied the wavelength-, time-, and intensity-dependence of the 3<sup>rd</sup>-order nonlinear optical response of As<sub>2</sub>Se<sub>3</sub> chalcogenide glass. Bulk samples were characterized using a wavelength-tunable z-scan system, over the range 1200-1600 nm. Thin film samples were characterized using an ultrafast time-resolved differential optical Kerr effect (DOKE) experiment, fed by 125 fs pulses centered at 1425 nm. The z-scans revealed only slight variation in the optical Kerr coefficient n<sub>2</sub> over the wavelength range studied. The DOKE experiment confirmed that the nonlinear response is predominately electronic, with response time limited by the experimental setup. For the same beam intensity, DOKE and z-scan measurements were in good agreement. The optical Kerr coefficient extracted from DOKE measurements at varying pump beam intensity showed intensity-dependent behavior, which can be attributed to fifth and higher order nonlinearities.