The low ac- and dc-field magnetic susceptibilities of hexagonal YbMnO3 single crystal have been measured along the ab plane and along the c axis (χab,χc). The antiferromagnetic Néel temperature TN is well signaled by a cusp in the temperature dependence of χc but no features are visible in χab. A remarkable anisotropy of paramagnetic susceptibility and the extrapolated Curie–Weiss temperature are observed and related to the quasibidimensional magnetic structure of YbMnO3. Below TN magnetic irreversibility sets, reflecting the presence of a weak ferromagnetic response. Possible scenarios for the origin of the weak ferromagnetism are discussed.