Abstract: The in vitro activity of three plant extracts; Artemisia cina, Peganum hormala and Calendula micrantha was investigated against Ascaridia galli adult worms. In vitro treatment of A. galli worms with different concentrations of each extract revealed potency of C. micrantha over the other two extracts as judged by the calculated LD50 values. These values were 2.66 ppm for C. micrantha, 33.7 ppm for P. harmala and 48.98 ppm for A. cina. The impact of the most potent extract, C. micrantha on A. galli worms was detected by scanning electron microscopy. C. micrantha treated worms showed enlargement and destruction of lips with subsequent damage of buccal cavity organelles. Moreover, papillae were disturbed and the amphids structures were lost. The cuticle showed wrinkled surface with loss of striations. Also, the cloacal structures were affected.