C-reactive protein (CRP) is an acute phase protein often used as a biomarker for inflammation related to acute trauma or chronic illness. Animal studies showing elevations in CRP following events such as road transport and moving to new housing suggest that CRP fluctuations may indicate how behavioral stress affects animal welfare. As part of a study about behavioral opportunities, salivary CRP was measured in three zoo-housed western lowland gorillas (Gorilla gorilla gorilla) to assess potential antiinflammatory effects of a foraging manipulation. Although the foraging conditions did not significantly affect CRP concentrations, an agonistic encounter—typical of the posturing that occurs among adolescent male gorillas—resulted in very minor injuries to one gorilla. Concentrations of salivary CRP increased over seventeen-fold for this gorilla, although his wounds were superficial and did not require veterinary treatment. Although animal care staff did not observe any wounds on the other two gorillas, CRP concentrations approximately doubled for both of them after this event, exceeding more than two standard deviations above their respective baselines. C-reactive protein was also correlated among individuals across the study period and with fecal glucocorticoid metabolite concentrations. These data provide first validation of CRP as a measure of the acute-phase response to injury in a gorilla and suggest that CRP may also fluctuate in response to social stressors, such as agonistic encounters. Salivary CRP may be a useful biomarker for several states that can contribute to negative welfare, including injury and social stress. These preliminary data should encourage additional investigations of CRP as a novel indicator of gorilla welfare.