Pentastomids are the most common endoparasite that infects the respiratory tracts of saurapsid reptiles, such as crocodilians. In this study we examined lung pentastomid parasitism in the American alligators, Alligator mississippiensis from northern Florida and southern Louisiana, U.S.A. (partitioned into the Louisiana West Zone and Louisiana East Zone) to determine the potential effects of alligator gender, size, and location on pentastomid distribution and abundance. In total, 1,405 lung pentastomids identified as Sebekia mississippiensis were found in 69 alligators (81.2% prevalence). Male alligators were found to have a higher pentastomid prevalence and intensity in comparison to females, which may be the effect of disparate life-history traits between the sexes and the larger size of males. Host size classes were found to be a significant trait influencing parasitism, as pentastomid prevalence and intensity increased in conjunction with alligator maturation. Our results also indicated that S. mississippiensis has a higher prevalence among Louisiana West Zone alligators, whereas the intensity was found to be higher among Florida alligators. Variation of intermediate host abundance is likely the primary cause for the differing pentastomid distribution among study locations. As such, these data further our understanding of the patterns of alligator pentastomiasis.