Glucocorticoids and melatonin show immunomodulatory functions, acting as stimulators and suppressors of the immune response, depending on the context. In amphibians, there are still few studies on this immune-endocrine interaction in an inflammatory context, all of them under captivity conditions. Evaluating how these animals react in the field to an immune challenge would reveal relevant information regarding how immune-physiological parameters are modulated in natural conditions. This study aimed to evaluate the effect of lipopolysaccharide (LPS) injection at early (9-10 pm) and late night (12-1 am) of toads (Rhinella icterica) recently captured in their natural habitat in Atlantic Forest. The following parameters were evaluated: plasma bacterial killing ability, plasma corticosterone, melatonin, and testosterone levels, and gene expression of cytokines and complement system protein (interleukin[IL]-1β, IL6, IL10, interferon-γ, C1S) in the spleen, two hours post-injections. LPS-injection induced an increase in corticosterone plasma levels and the gene expression of IL1β, while no changes were found in the other variables. During the early night, LPS-injected toads had upregulation of IL1β compared with the saline-injected ones, evidencing that LPS induced an inflammatory response. Our results are associated with the first stage of the inflammatory response, and studies evaluating further steps of the immune response might lead to a better understanding of the immune-endocrine relations in amphibians.