From 1918 to 1925 he headed the botanical section of the Caucasian Museum in Tbilisi. From 1925 to 1930 he was professor at the Tomsk State University, where he held a chair of morphology and plant systematics. From 1930 he worked in the Komarov Botanical Institute of the Academy of Sciences of the USSR (from 1938 to 1949 as director) and from 1945 to 1958 also as professor at Leningrad University. From 1946 to 1963 he was vice-president of the Botanical Society of the USSR. Shishkin's herbarium included more than thirty thousand samples, the majority of which are held in Tomsk.
