Preliminary investigation of carbonaceous sediments from the late Proterozoic Tindir Group, east-central Alaska, reveals the presence of abundant single-celled and spherical colonial nannofossils interpreted to represent blue-green algae. Similar micro-organisms, particularly Sphaerocongregus Moorman, have been reported from the late Proterozoic Hector Formation of southwestern Alberta, Canada. The fossils reported here come from beds tentatively considered to represent the upper Tindir Dolomitic Sandstone and Shale member, stratigraphically above the Basalt and Red Beds member, for which an age of no more than 850 m.y. has been suggested. However, it is possible that the fossiliferous sequence is correlative with the lower Tindir Dolomite and Shale member which immediately underlies the Basalt and Red Beds member, and which contains a stromatolitic structure known in beds 950 m.y. old and older elsewhere.