More than a decade of field surveys of Caliaeschna microstigma (Schneider, 1845), at the north-western edge of species' distribution in Bosnia & Herzegovina, Croatia, and Montenegro recorded its presence at 135 localities, of which 107 were previously unknown. Our sampling located populations north-west of the species' previously known range limit. Literature and new data showed that the species was most frequently observed in karst springs (42 % of all known localities) and streams (34 %) and, to a lesser extent, also in rivers (24 %). Although it was observed over a wide range of altitudes, from sea level to mountainous regions (865 m a.s.l.), 72 % of the localities were below 200 m a.s.l., and 43 % below 50 m a.s.l. Reproduction attempts and/or successful reproduction was recorded at approximately half the localities (53 %, n = 71), mostly in the Mediterranean but also in the Alpine biogeographical region. Most of the localities with C. microstigma present are suffering from various anthropogenic threats, such as domestic and constructional waste disposal, capture of spring water, and urban and agricultural impacts. This study contributes to a better understanding of the species' distribution and provides new insight into its habitat and microhabitat preferences.