Clustered regularly interspaced palindromic repeats (CRISPR)-associated (Cas9) technology has proven a formidable addition to our armory of approaches for genomic editing. Derived from pathways in archaea and bacteria that mediate the resistance to exogenous genomic material, the CRISPR-Cas9 system utilizes a short single guide RNA (sgRNA) to direct the endonuclease Cas9 to virtually anywhere in the genome. Upon targeting, Cas9 generates DNA double-strand breaks (DSBs) and facilitates the repair or insertion of mutations, insertion of recombinase recognition sites, or large DNA elements. Here, we discuss the practical advantages of the CRISPR-Cas9 system over conventional and other nuclease-based targeting technologies and provide suggestions for the use of this technology to address immunological questions.