Objectives: The present study was undertaken to evaluate the immunomodulatory (IM) activity of IM-133N, a herbal combination in various immunotherapeutic experimental models. Methods: The IM activity of IM-133N was evaluated against three experimental models namely, effect of IM-133N against Escherichia coli (E. coli)-induced abdominal sepsis in mice, and carbon clearance test was performed in Wistar albino rats to evaluated the phagocytic potential of IM-133N, in addition IM-133N was evaluated for its immunoglobulin enhancing potential in rats, where the immunoglobulin levels were measured by zinc sulphate turbity (ZST) test. Further, IM-133N was subjected for detailed liquid chromatography-mass spectrometry (LC-MS)/MS analysis to identify the probable active constituents present in it. Results: The findings of the present study has demonstrated very promising IM property of IM-133N in all the experimental models. Briefly, pretreatment with IM-133N at 125, 250, 500 and 1,000 mg/kg, p.o. doses had protected the mice against E. coli-induced abdominal sepsis and mortality, further the effect of IM-133N was found to be significant and dose-dependent. In support of this, in another study administration of IM-133N showed a significant and dose-dependent increase in serum immunoglobulin levels, estimated by ZST test. In line with the above findings, in the carbon clearance test the low doses (125 and 250 mg/kg, p.o.) of IM-133N increased the rate of carbon clearance, whereas the higher doses (500 and 1,000 mg/kg, p.o.) did not sustain the response, and saturation effect was considered as one of the possible reason for futility of higher doses for IM-133N. In addition, A detailed LC-MS/MS analysis of IM-133N showed 17 bioactive phytochemical constituents: namely, apigenin, chaulmoogric acid, mesquitol, quercetin, symphoxanthone, salireposide, ${\beta}$-sitosterol, nonaeicosanol, ${\beta}$-amyrin, betulic acid, oleanolic acid, symplososide, symponoside, symploveroside, symplocomoside, symconoside A and locoracemoside B. Conclusion: These findings suggest that IM-133N possesses significant IM activity and, hence, could be useful for eradicating opportunistic disease-triggering pathogens via immunotherapeutic mechanisms. The findings also suggest IM-133N may also useful in other immunity disorders.