In the present paper, the authors provide a comprehensive description of the morphology and biology of all developmental stages of the rove beetle Philonthus spinipes Sharp, 1874, which is regarded as an adventive species in Europe. Material for study was obtained through rearing from eggs laid by wild caught adults. The most important diagnostic characters distinguishing the egg of P. spinipes from the eggs of other species of Philonthus Stephens, 1829 are: posterior pole trapezoidal in shape and with c. 800 aeropyles forming 12–13 longitudinal rows each bearing 60–65 aeropyles. The final larval stadium (L3) is distinguished by: anterior margin of nasale with seven teeth; epipharynx with cuticular processes anteriorly forming uniform row; anterior tibia with two combs of 9 and 8 setae; urogomphus one-segmented, thin and very long; apical seta of urogomphus minute. Compared with L3, the first larval stadium (L1) differs in its dimensions, body colour and shape, as well as the antennal structure, nasale, epipharynx and mandible, and the number of setae on the legs and on the thoracic and abdominal sclerites. The pupa of P. spinipes possesses all the characters typical of the subtribe Philonthina. It is very much larger than the pupae of other Philonthus species; further differences include a pronotum with 14 or 16 setiform projections, antennae extending to one-third of the elytral length, and hind tarsi protruding well beyond the posterior margin of segment III. The average duration of the life cycle of P. spinipes is 28 days, which is much shorter than that of other Philonthus species inhabiting similar environments. The current knowledge regarding the zoogeography of P. spinipes is summarized. Questionable distributional data in the literature have been verified, leading to the first record of P. spinipes in Serbia and the removal of this species from the list of rove beetles of Armenia. The precision and detail of this paper place P. spinipes among the rove beetles with the best-known natural history. Importantly, this focused study may allow for a better understanding of the expansion of this species across the Palearctic.