The late Pliocene-Pleistocene paleoenvironment has been reconstructed based on three-dimensional seismic data from the southwestern Barents Sea continental margin. During the late Pliocene-early Pleistocene, continental slope sediments were predominantly deposited from meltwater overflows and underflows. The seismic stratigraphy of the early-middle Pleistocene shows both glaciomarine sediment input from channelized meltwater discharge and the first indications of large debris-flow deposits on the continental slope, originating from input of subglacial deformation till eroded and transported by ice streams. During the middle-late Pleistocene, large debris flows dominated the slope succession. From the above results we infer the following evolution in the Barents Sea: (1) a temperate Barents Sea Ice Sheet with channelized meltwater flow developed during the late Pliocene-early Pleistocene; (2) alternating glacial periods of ice with channelized meltwater flow and the first periods of ice, including ice streams, characterized the early and middle Pleistocene; and (3) more polar ice conditions and a Barents Sea Ice Sheet that mainly included large ice streams, with little or no channelized meltwater flow, occurred in the middle and late Pleistocene.