We obtained material from the Puerto Escaño section (southern Spain) to study the Jurassic/Cretaceous (J/K) boundary interval. The same samples had already been processed for magnetostratigraphic studies and biostratigraphic zonation based on calpionellids and ammonites (Pruner et al. 2010), but not for calcareous nannofossils. The aim of this study was to process the samples using micropalaeontological analysis and to compare and calibrate results for calcareous nannofossils with existing magnetostratigraphic and other biostratigraphic data. The calcareous nannofossil assemblage was dominated by the genera Watznaueria, Cyclagelosphaera, Nannoconus, Conusphaera and Polycostella. Several nannofossil bioevents were recorded on the basis of the distribution of stratigraphically important taxa, including zonal and subzonal markers. Based on the lowest occurrences (LO) of M. chiastius, N. globulus minor, N. wintereri, N. steinmanii minor, N. steinmannii steinmannii, N. kamptneri minor and N. kampteri kamptneri, two nannofossil subzones (NJT 15b, NJT 17a) and two nannofossil zones (NJT 16, NK-1) were recognized. The paper introduces new palaeoecological data based on geochemical analysis and macrofauna occurrences.