Lernaea cyprinacea infestation is considered a serious economic problem in the fish market. An assessment to control this parasite is needed to manage this problem. The Illicium verum oil extract has considerable antioxidant activity and scavenges 96.22% of free radicals; the high antioxidant activity refers to the phenolic content presence. The extract contains minerals, especially K, fibers, and dry matter. So, the Illicium verum ingredients were tested against this copepod for in vitro and in vivo investigation with the assessment of the treatment trial using a scanning electron microscope and evaluating the change in different immunological genes in goldfish. Female parasitic L. cyprinacea worms were blackish and hairy. The in vitro study on L. cyprinacea adults using star anise revealed that the LC50 was 12.5 and 25 µg/mL for 2 and 1 h exposure periods, respectively. Interleukin (IL-1β) and IL-6 were grossly upregulated in C. auratus-infested skin by L. cyprinacea after treatment by 1 week, then declined after 3 weeks. In contrast, TNF-α was 18 folds upregulated in the first week after treatment, with a decline after 3 weeks. In conclusion, star anise is recommended as a safe and economical agent for controlling L. cyprinacea infestation in fish.