Short linear motifs (SLiMs) are important interaction modules of intrinsically disordered proteins. Characterized with structural flexibility and short sequence, SLiMs are promiscuous and mediate transient, reversible protein-protein interactions. With the advancement of experimental measures and motif-search tools, an increasing number of short linear motifs are being discovered. The BH3 domain of the Bcl-2 family, for example, was recently redefined as a short linear motif. Here, we review the characteristics of SLiMs in structure, function and evolution. Subsequent studies about their functions will shed new light on cell signaling networks researches, therapeutic targets identification and drug discovery.