Information concerning the pulmonary toxicity of oxaliplatin with infusional 5-fluorouracil plus leucovorin (FOLFOX) is very limited. We herein report the case of a patient with FOLFOX-induced interstitial pneumonia. An 82-year-old man with unresectable colon cancer liver metastases was referred to our department for chemotherapy with the FOLFOX protocol. After the administration of ten cycles, he visited our outpatient clinic with a 2-week history of coughing and shortness of breath; he was afebrile. A chest radiograph showed reticular shadows with ground-glass opacities mainly involving the middle and lower zones of the right lung. Computed tomography depicted ground-glass opacities with superimposed reticulation in the right lung. A diagnosis of FOLFOX-induced interstitial pneumonia was made based on the clinical course and imaging findings. The symptoms disappeared within 3 days after the cessation of the FOLFOX regimen and the initiation of high-dose corticosteroid treatment. Two months after the initiation of the corticosteroid treatment, complete remission of the radiological abnormalities was confirmed; thereafter, interstitial pneumonia did not recur despite the reintroduction of 5-fluorouracil/leucovorin alone, suggesting that 5-fluorouracil/leucovorin alone was not responsible for the development of the interstitial pneumonia. Thus, oxaliplatin, alone or in combination with 5-fluorouracil/leucovorin, may have caused the interstitial pneumonia in this patient. Once interstitial pneumonia has occurred, cessation of the regimen is mandatory, and high-dose corticosteroid treatment is commonly given to rescue patients from this potentially lethal complication.