Streptococcosis is one of the most important diseases in aquaculture, causing high rates of mortality in fish. ArtinM, an immunostimulant obtained from jackfruit (Artocarpus integrifolia) seed extract, enhances the innate immune response. The aim of this study was to examine the action of ArtinM on neutrophil haptotaxis to the peritoneal cavity of juvenile Nile tilapia (Oreochromis niloticus) inoculated intraperitoneally with Streptococcus agalactiae. After establishing the LD50 of S. agalactiae and the effective dose of ArtinM, 120 animals randomly distributed in 12 aquaria were divided into the following four treatment groups: G1, control; G2, via the intraperitoneal (i.p.) route inoculation with ArtinM; G3, i.p. inoculation with S. agalactiae and G4, i.p. inoculation with ArtinM and challenge with S. agalactiae. Six and 24 hours after treatment, the fish were sacrificed and peritoneal exudate and caudal vein blood samples were collected for analysis of the total number of leukocytes and neutrophils. To establish the optimal ArtinM concentration, the results were analyzed with a chi-square test at a 1% significance level. The experimental inoculation and challenge results were analyzed with the SASM-Agri software developed by Canteri et al. (2001) using the Scott-Knott’s test at a 5% significance level. The results of this study showed that i.p. inoculation with 1.0 μg ArtinM/animal has an effect on neutrophil haptotaxis to the peritoneal cavity in juvenile Nile tilapia. Therefore, ArtinM might represent a suitable prophylactic alternative in juvenile Nile tilapias inoculated with S. agalactiae.