Organizing pneumonia (OP) is a pattern of pulmonary tissue repair injury. It can be cryptogenic or a response to a specific lung injury. Radiation therapy is a potential cause of secondary OP, especially after breast irradiation. The lesions may appear anywhere in the lung parenchyma with no relation to the irradiated side. Corticotherapy is the mainstay of treatment and prognosis is generally favorable. We describe a case of a female patient previously diagnosed with breast cancer who developed secondary OP within six months of postoperative radiotherapy. Initial diagnosis was challenging due to the rarity of the disease as well as management that required close follow-up with careful tapering given the frequent relapses associated with the withdrawal of corticosteroid therapy. The reported case emphasizes the importance of recognizing secondary OP as a rare complication of postoperative radiotherapy for breast cancer and puts into view the complexity of its management.