Pasteurellaceae form a family of Proteobacteria and are the only member of the order Pasteurellales. Pasteurellaceae are Gram-negative, rod or coccoid, immotile bacteria that differ from Enterobacteriaceae in the presence of oxidase and from most similar bacteria in the absence of flagella.
Some species are pleomorphic and change their cell shape over time; in older cultures, the formation of filaments (cell filaments) can often be observed.