The Great Bustard population in Xinjiang Province, the Chinese stronghold of Otis tarda tarda, is suspect to be declining, but little is known about its trends and numbers. Using the same methods, we compared two former published counts from the province (1988 and 1992) with ours (2013–2016), exhaustively covering the two known bustard areas of Tacheng (summer) and Qapqal (winter). A strong decline (92%) is reported, with a minimum 19 birds found in Tacheng and none in Qapqal. Cooperation between scientists is needed to study the causes of decline in O. T. tarda in Xinjiang and elsewhere.—Wang, M., González, M.A., Yang, W., Neuhaus, P., Blanco-Fontao, B. & Ruckstuhl, E.K. (2018). The probable strong decline of the Great Bustard Otis tarda tarda population in north-western China. Ardeola, 65: 291–297.