Background: Studies on nematode taxa remain poorly described in cold blooded animals, with rareness of data on the helminth community of Egyptian ones, especially lizards. The available literatures are mostly restricted to ecological studies rather than descriptive ones. Objective: To identify and give full description for nematodes that inhabit the Desert Agama, Trapelus mutabilis (T. mutabilis) caught from El-Dabaa desert, Egypt. Material and Methods: Nineteen Agama lizards having the characteristic morphological criteria of T. mutabilis were dissected and examined for parasitic infection. Gastrointestinal nematodes were collected, fixed and identified using light microscopy. Those subjected for scanning electron microscopy (SEM) were dried, coated and examined. Results: Seven out of nineteen dissected lizards were found to be infected with the nematode Thubunaea pudica (T. pudica) (Family: Physalopteridae). They were collected from the stomach and small intestine of T. mutabilis. The main characteristics of adult T. pudica are: symmetrical anterior cephalic structure similar in both sexes, vulva is situated in the first tenth of the body, the tip of male tail ends beyond well-developed caudal alae with 32 true caudal papillae and two subequal stout spicules. Conclusion: The study added the first fully described details for T. pudica using both light and SEM. Moreover, T. mutabilis lizard represents a new host record for T. pudica in a new geographic locality El-Dabaa desert as there are no reports of this species recorded from Egypt.