The overexpression of efflux pump is one of the most important multidrug-resistant mechanisms in Acinetobacter baumannii (A. baumannii). The understanding of their complicated mechanisms will help to find out efficient coping strategy. So far four prominent families of efflux transporters in A. baumannii have been reported, including resistance-nodulation-cell division (RND) superfamily, major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE) superfamily, and small multidrug resistance (SMR) superfamily. They can be divided into chromosomally encoded efflux system and acquired efflux system. The substrates are also distinguished among different efflux transporters. In this review, the classification, function and regulation of efflux pumps in A. baumannii are described.