An unusual Gram-negative, catalase- and oxidase-positive, rod-shaped bacterium isolated from different clinical samples from two monkeys (Callithrix geoffroyi) was characterized by phenotypic and molecular genetic methods. The micro-organism was tentatively identified as a Pseudomonas species on the basis of the results of cellular morphological and biochemical tests. Fatty acid studies confirmed this generic placement and comparative 16S rRNA gene sequencing studies demonstrated that the unknown isolates were phylogenetically closely related to each other (100 % sequence similarity) and were part of the ‘Pseudomonas fluorescens intrageneric cluster’. The novel bacterium, however, was distinguished from other phylogenetically related species of Pseudomonas by DNA–DNA hybridization studies and biochemical tests. On the basis of both phenotypic and phylogenetic findings, it is proposed that the novel Pseudomonas isolates are classified as Pseudomonas simiae sp. nov. The type strain of P. simiae is OLi^T (=CCUG 50988^T=CECT 7078^T).