The article presents the under-explored St Petersburg period in the work of Gustav Mootse, famous Estonian artist, founder of Estonian book graphics and ex libris master. Upon a thorough archival research of illustrated periodicals, the authors have revealed unknown images by Mootse. Based on those, they make conclusions on stages in Mootse’s creative evolution, show a progressive growth in his standing in St Petersburg periodicals, show his search for forms and experiments, and comment on specifics of his creative work.