Plant parasitic nematodes are dangerous pests that infect many agricultural crops including cucumber. A greenhouse experiment was conducted in the experimental farm of Botany and Microbiology Department, Faculty of Science, Al-Azhar University, to evaluate the efficient of Salicylic acid and Fosthiazate (melotherin®) as abiotic elicitors and Serratia marcescens as biotic elicitor against root-knot nematode Meloidogyne incognita infecting cucumber plants. Results indicated that, applying Fosthiazate (melotherin®) for 96 hours obtained the most mortality percentages of M. incognita 2nd juveniles invitro followed by salicylic acid then Serratia marcescens by 74.2%, 27.87% and 13.19 % respectively. Under greenhouse conditions, similar results obtained where Fosthiazate (melotherin®) was the most potent treatment reducing nematode galls, egg masses, females, and developmental stages in infected cucumber roots by 86.15%, 93.89%, 67.81% and 73.22% respectively as well as 2nd juveniles in the soil by 79.48%, followed by Salicylic acid and Serratia marcescens respectively. Regarding plant morphological and biochemical parameters, application of Serratia marcescens followed by salicylic acid showed significant improvements in cucumber vegetative growth and yield as well as photosynthetic pigments and antioxidant enzymes. It could be suggested that application of Fosthiazate (melotherin®), Serratia marcescens and Salicylic acid could be commercially used as safe, effective and cheap nematocidals against root-knot nematode.