The braconid genus Dyscritulus Hincks is a small member of the subfamily Aphidiinae, distributed in Europe and Central Asia. All its species are highly specialized parasitoids of aphids of the genera Drepanosiphum Koch and, probably, Periphyllus van der Hoeven which are mostly associated with maple and sycamore trees (genus Acer). Upon examination of specimens from the Naturalis Biodiversity Center, Leiden, we unexpectedly noted unusual variability in morphological characters compared to other known Dyscritulus species. Further inspection of other material previously identified as Dyscritulus planiceps Marshall, 1896 revealed additional specimens with the same morphological variability. Here we describe a new species of the genus, Dyscritulus europaeus sp. nov., associated with Drepanosiphum aphids on Acer.