Organisms with separate sexes usually exhibit sexual dimorphism, meaning morphological differences between the male and female individuals. Even though not as common as in animals, plants can also express sexual dimorphism. The study of sexually dimorphic traits is important because they influence the growth, physiology, pollinator visitation, and adaptation of different plant populations. A type of sexual dimorphism called sexual dichromatism is expressed by differences in color between the sexes. It is common in birds and reptiles and has not been documented in plants. Our research is based on a rare dioecious cactus called Wolf’s cholla (Cylindropuntia wolfii, Cactaceae), that is distributed at the border of California and Baja California. This species serves as a good model to study sexual dimorphism and dichromatism as it has a functionally dioecious sexual system with six different flower color morphs within the same region. The main goal of our study is to identify sexually dimorphic traits including dichromatism in the male and female flowers of C. wolfii. To identify sexual dimorphism, we measured several categorical and quantitative factors that potentially influence pollinator visitation, such as flower color, UV emission, autofluorescence, filament color, tepal shape, flower display diameter, tepal length, tepal width, and number of flowers per plant. The differences between the sexes were measured and assessed for significance using statistical analysis e.g., ANOVA. Our results suggested that C. wolfii has sexual dichromatism as male flowers are usually associated with brighter flower color morphs such as green and yellow. These features can make the male flowers more attractive to pollinators than females and it is predicted to be a consequence of intrasexual competition in dioecious species. Furthermore, we observed fluorescence dichromatism where female flower anthers fluoresce more than male flower anthers as a result of early degeneration of anther walls in females when they abort the male sex. Our study is the first to report floral sexual dichromatism and fluorescence dichromatism in a dioecious plant and will be a pioneer for future dichromatism studies in plants.