This article provides new morphological data about Mesocriconema involutum (Loof, 1987) Loof, 1989, a very rare European nematode species. This is the first report on its occurrence in Poland and the third record in Europe. Specimens of M. involutum described in this article were collected from the rhizosphere of grass on the bank of Lake Kielno (northern part of Poland). The research allowed to determine the presence of two projections on the anterior vulval lip, which previously had not been described for this species. A detailed description of the tail's terminal annulus is also given.