A survey of foliar pathogens of watermelon based on two-stage cluster sampling was conducted on commercial farms in South Carolina in spring 2015, spring and fall 2016, and fall 2017. In total, 60 fields from 27 different growers in seven counties representing the main watermelon-producing areas in the state were sampled, using a stratified two-stage cluster sampling approach. In the sampling design, counties corresponded to strata, growers to first-stage clusters, and fields to second-stage clusters. In each field, 100 symptomatic leaves were collected at five equidistant sampling points along four transects encompassing a square shape of 2,500 m2. After collection, pathogens were identified based on reproductive structures formed on leaves during >12 h incubation. Estimates were obtained for the statewide probability of pathogen occurrence and associations between pathogen pairs. Six fungal pathogens, Stagonosporopsis spp., Podosphaera xanthii, Cercospora citrullina, Colletotrichum orbiculare, Myrothecium sensu lato (s.l.), and Corynespora cassiicola; the oomycete Pseudoperonospora cubensis; and three viral pathogens were identified on the examined leaves. With the exception of fall 2017, Stagonosporopsis spp. was the most prevalent pathogen in every season, followed by P. xanthii. The highest occurrence of P. cubensis was in spring 2015; it did not occur in 2016. The highest occurrence of C. orbiculare was in spring 2016; it did not occur in spring 2015. Myrothecium s.l. was the most common pathogen in fall 2017 and the second most common pathogen occurring by itself in fall 2016. The third most common pathogen in fall 2017, Corynespora cassiicola, was not observed in any other season. Eight of the 80 isolates of Stagonosporopsis spp. collected were identified as S. caricae, the rest as S. citrulli. All isolates of S. caricae were found in spring 2015 and originated from two fields in different counties. A total of three positive and five negative associations were found between pathogen pairs co-occurring on the same leaf. A positive association between Stagonosporopsis spp. and C. citrullina was the only significant association between pathogens found in two seasons, spring 2015 and spring 2016. Based on estimates of probability of pathogen occurrence across seasons, Stagonosporopsis spp. and P. xanthii are the most common pathogens on watermelons in South Carolina. This is the first report of C. cassiicola, S. caricae, and Myrothecium s.l. on watermelon in South Carolina.