This study investigated the immunomodulatory capabilities of the sub-chronic administration of Yoyo bitters in male Wistar rats. Eighteen rats weighing 86.2 +/- 4.43 g were randomly picked into three equal groups. The rats were acclimatized for 14 days, after which 0.308 and 0.462 mL kg(-1) b.wt. of Yoyo bitters were administered once daily to groups B and C respectively for 56 days, while group A received distilled water. The feed intake, body weight, blood glucose, interleukin 2 (IL-2), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha), haematological parameters, serum lipid profile and uric acid, liver reduced glutathione and malodialdehyde were determined. The feed intake, body weight and blood glucose concentrations were reduced (p < 0.05) at the doses. No changes were recorded in the concentration of serum IL-2 (p > 0.05), but IL-6 decreased (p < 0.05) in group B and increased (p < 0.05) in group C, while TNF-alpha were increased (p < 0.05) dose dependent. The haematological parameters were decreased at all the doses (p < 0.05), except the ESR, WBC and lymphocytes that were increased (p < 0.05) and platelets in group C (p < 0.05). The serum total cholesterol, TAG, LDL-C and atherogenic index were decreased (p < 0.05) and HDL-C increased (p < 0.05) in group B only. Serum uric acid was reduced (p < 0.05) in group B, but increased in group C with the concentration of liver MDA (p < 0.05). The study, therefore, established that a dose lower than the manufacturer's recommended dose presented the desired immunomodulatory activities and the habitual use of Yoyo bitters at the adult recommended dose calls for caution.