Six new acritarch species were observed during a high-resolution study on the upper Burdigalian to Serravallian (lower and middle Miocene) of the Porcupine Basin (Integrated Ocean Drilling Program Leg 307, off southwestern Ireland). The stratigraphical ranges and palaeoenvironmental preferences of the six new species were assessed. Cometesphaera bullatio gen. et sp. nov. is recorded from the upper Burdigalian to the lower Serravallian, while the range of Cymatiosphaera? deverteuilii sp. nov. is restricted to the upper Serravallian. Platycystidia manumii sp. nov. is recorded from the upper Burdigalian to the upper Langhian. Porcupinea collaris gen. et sp. nov. and Porcupinea indentata gen. et sp. nov. range from the upper Langhian to the lower Serravallian, and from the uppermost Burdigalian to the upper Serravallian, respectively. Pusillisphaera solaris gen. et sp. nov. is recorded from the from the upper Burdigalian to the upper Serravallian.