This study presents the micropalaeontological data (palynomorphs and ostracods) including index taxa to assign a precise age, and the palaeoecological evolution of the Aspiras Basin, south-east Kastamonu, northern Anatolia. The succession may informally be divided into a lower part including rich lignites interbedded with fine-grained sediments and an upper part which comprises lignite-free deposits such as mudrocks with dense gypsum and rare limestones. The sediments of the lower part were deposited in a wetland (i.e. peat-forming environment) showing oscillations of the lake level, whereas the upper part indicates the shoaling or closing phase of the lake. Early Miocene age is assigned to the Aspiras Basin due to the presence of index taxa such asLeiotriletes maximus,Dicolpopollis kockelii,Intratriporopollenites instructus,Caryapollenites simplex, and ostracodsPseudocandona praecoxandPotamocypris gracilis. Moreover, a new species of ostracod,Heterocypris aspirasensis, has been discovered. In the lowermost part of the succession, palynomorph spectra are dominated by spores such asLeiotriletes maxoides,L. maximus, andVerrutacosporites alienuswhile diverse pollen types, notably conifer pollen, attain high abundances further up in the succession. In the forested environment, the mixed mesophytic plants were less diverse. Low quantities of herbaceous taxa such asEphedrasp., Poaceae, Amaranthaceae, Asteraceae-Asteroideae, and Asteraceae-Cichorioideae indicate the limited occurrence of open areas. During the Early Miocene, a warm and moist climate prevailed according to quantitative palaeoclimate data and the presence of the mega-mesothermic taxa such as Taxodioideae, Mastixiaceae,Engelhardia, Sapotaceae, andCalamus.