Agmatine is a novel neuromodulator that plays a protective role in the CNS in several models of cellular damage. However, the mechanisms involved in these protective effects in neurodegenerative diseases are poorly understood. Fourier transform infrared (FTIR) spectroscopy analysis detects biomolecular changes in disordered cells and tissues. In this report, we utilize FTIR spectroscopy to characterize the changes in rotenone-induced damage in neuronal-like differentiated SH-SY5Y neuroblastoma cells in the presence or absence of agmatine. The analysis of the FTIR spectra demonstrates significant alterations in rotenone-treated cells, whereas the FTIR spectra obtained after pre-incubation with agmatine (250 nM) significantly reduces these redox alterations and more closely resembles those of the control cells. In particular, rotenone-damaged cells demonstrate spectral alterations related to amide I, which correspond to an increase in β-sheet components, and decreases in the amide II absorption intensity, suggesting a loss of N-H bending and C-N stretching. These alterations were also evident by Fourier self-deconvolution analysis. Thus, rotenone-induced increases in the levels of stretching vibration band related to the protein carboxyl group would account for a significant amount of misfolded proteins in the cell. Agmatine effectively reduces these effects of rotenone on protein structure. In conclusion, antioxidant and scavenging properties of agmatine reduce rotenone-produced cellular damage at the level of protein structure. These, together with other previous observations, demonstrate the therapeutic potential of agmatine in the treatment of Parkinson's disease.