A new species of Ceratocystis with a Chalara anamorph was observed to cause black stains on the cut surfaces of recently felled Eucalyptus obliqua logs in south-western Tasmania, Australia. It is described as C. moniliformopsis because of its similarity to C. moniliformis in morphology of ascospores and perithecia. This is a homothallic species and is characterised by a thick perithecial peridium, ovoid perithecia and disciform-based perithecial necks with convergent ostiolar hyphae. The perithecia are covered with the following two types of ornamenting hyphae: hyaline, thin-walled, aseptate, tubular hairs and dark brown, thick-walled, ampliform to conical setae. Its Chalara anamorph has the following two types of conidiogenous cells: hyaline, cylindrical tapering phialides and pigmented, cupulate or divergent phialides with percurrent proliferation. The latter is a unique type of conidiogenous cell that has not been observed in this genus before the present study.