The objective of this paper is to determine the effect of levamisole (LEV) immunoglobulin concentration in the serum of boars exposed to three-day stress induced by the adrenocorticotropic hormone (ACTH). Boars were assigned to four groups (n=7). The first group received LEV for three days (2.5 mg/kg BW), the second group received ACTH (10 g/kg BW) for three days and the third group received LEV for three consecutive days and ACTH on the three following days (2.5 mg/kg BW ; ACTH 10 g/kg BW). The control group received saline solution (1 mL) during the experiment (six days). Concentrations of total protein, globulin, albumin and immunoglobulin concentration (IgG, IgA and IgM) were determined during levamisole, ACTH and levamisole + ACTH combined treatment administration, and during the 16-day post- administration period. Total protein levels were significantly increased during the stress period and over the next sixteen days (p0.01 to p0.0001, respectively) in the ACTH group of boars. However, total protein levels were significantly elevated in the LEV+ACTH group on day 1 and 2 of ACTH injection (p0.05 and p0.001) and on day 5 and the last day of measurement (p0.001 and p0.01). However, the three-day administration of levamisole (LEV) stimulated a statistically significant increase of protein concentrations compared to control values after levamisole treatment, on days 2 and on days 11, 15 and 24 (p0.01, all). Levels of serum albumin were not affected with levamisole or ACTH treatment. According to determined total protein concentrations, globulin concentrations were significantly increased throughout and after the ACTH treatment in the second group (p0.01 to p0.0001, respectively). Also, globulin concentrations were significantly elevated in the LEV+ACTH group throughout the three-day ACTH treatment and in the 16-day post-administration period (p0.05 to p0.01, respectively). The three-day levamisole administration resulted in an increase of globuline concentrations (LEV). However, there were no statistically significant differences in comparison to control pigs. ACTH treatment significantly elevated serum IgG concentration during the stress period (p0.001 to p0.0001, respectively) and over the next 16 days (p0.01 to p0.0001, respectively). However, in the LEV+ACTH group of boars, IgG levels were significantly elevated on days 1 and 3 of ACTH injection (p0.05 and p0.01) and days 1 and 5 in the post-treatment period (p0.01 and p0.05). Administration of levamisole (LEV) had no significant impact on IgG levels compared to the control boar group. However, a statistically significant increase in IgA concentrations in boars treated with levamisole (LEV) was determined on day 2 (p0.02) and day 11 (p0.05) after administration of levamisole compared to animals of the LEV+ACTH group. Furthermore, boars receiving levamisole before stress induction (LEV+ACTH) on day 5 after stress induction had IgM concentrations statistically significantly higher (p0.05) than animals treated only with ACTH. These results show that levamisole may stimulate the immune system in swine and immunoglobulin in the serum of boars exposed to stress.