Technical Abstract: Caladium (Caladium hortulanum Birdsey) is an important aroid widely used in the ornamental plant industry. Concerns have been raised about possible loss of genetic diversity due to a drastic decline in the number of cultivars in the last century. This study assessed genetic diversity and relationships among caladium cultivars and species accessions. Forty-five major cultivars and 14 species accessions were analyzed based on 297 DNA fragments produced by the target-region amplification polymorphism marker system. A low level of diversity (44.4% polymorphism) was exhibited in cultivars, while a high level of diversity (96.8% polymorphism) was present among seven accessions of Caladium bicolor (Aiton) Vent., Caladium marmoratum Mathieu, Caladium picturatum C. Koch, and Caladium schomburgkii Schott. A small percentage (7.6%) of DNA fragments was present in cultivars but absent in the seven species accessions, while a high percentage (32.2%) of DNA fragments was present in the seven species accessions but absent in cultivars. Cultivars shared a higher level of similarity at the molecular level with an average Jaccard coefficient at 0.802, formed a large group in cluster analysis, and concentrated in the scatter plot from a principal-coordinate analysis. Two accessions of C. bicolor and C. schomburgkii were very similar to cultivars with Jaccard similarity coefficients from 0.531 to 0.771, while the rest of the species accessions had small similarity coefficients with cultivars (0.060 to 0.386). Caladium steudnirifolium Engler and Caladium lindenii (Andr'e) Madison were very dissimilar to C. bicolor, C. marmoratum, C. picturatum, and C. schomburgkii, with Jaccard similarity coefficients from 0.149 to 0.237 (C. steudnirifolium) and from 0.060 to 0.118 (C. lindenii). There is a limited amount of molecular diversity in caladium cultivars, but the great repertoire of unique genes in species accessions could be used to enhance the diversity in future cultivars and reduce potential genetic vulnerability.