We introduce a classification system for the sexual modes of modular (clonal and colonial) animals which incorporates both spatial and temporal components of modular sexuality. After explaining and illustrating each potential sexual mode, we compare the prevalence patterns of sexual modes among modular animals, unitary animals, and flowering plants. Our conclusions are: (1) There are far more potential colonial modes of sex, and more clonal modes of sex, than there are unitary modes of sex. This is a function of the tri-level and bi-level organization, respectively, of colonial and clonal animals, in contrast to the single level of unitary ones. (2)Only five of ten potential colonial modes of sex have known examples, while only four of six potential clonal modes of sex have known examples. (3) The sexual mode of many modular metazoans is not known, in part because of a previous lack of terms by which to refer to modular sex at all its levels of expression. (4) Comparison of clonal and colonial animals reveals that genet gonochorism is nearly twice as common in clonal as in colonial animals. Genet hermaphroditism achieved by gonochoric modules of both sexes (monoecy) is about three times as common in colonial as in clonal animals. (5) Comparison of unitary and modular animals reveals that genet sequential hermaphroditism, while moderately common among unitary animals, has virtually no examples among modular ones. Genet gonochorism is also more prevalent among unitary animals than among modular ones (and conversely, genet simultaneous hermaphroditism is far more prevalent among modular than unitary animals). (6) Despite striking differences in the prevalence of different sexual modes at the genet level, clonal, colonial, and unitary animals display very similar patterns of sexual mode when examined at the modular level. (7) Comparison of seed plants and modular animals reveals that both genet gonochorism and monoecy are considerably rarer in plants than in modular animals. Sequentially hermaphroditic genets may be more common among plants than among modular animals. Some sexual modes in our classification may be represented among plants, but not among animals.