Metastatic prostatic adenocarcinoma presenting as a primary lung disease is rare. We present a 52-year-old male with a 3-month history of cough, shortness of breath, and weight loss with clinical and radiological findings suggestive of a primary lung disease: Bilateral interstitial and alveolar opacities with blunting of the costophrenic angles, multiple diffuse foci of consolidations and nodules, predominantly subpleural and located in the lower lobes, and diffuse interlobular septal thickening and peribronchial thickening. The patient underwent bronchoscopy and bronchoalveolar lavage (BAL) was obtained. Cytospin smears were diagnostic for a low-grade adenocarcinoma. Clinically, the patient had elevated serum prostate-specific antigen (PSA) levels greater than 5,000 ng/mL. Because of this, immunocytochemistry for PSA was performed which was positive, confirming the diagnosis of metastatic prostatic adenocarcinoma. This unusual case of metastatic adenocarcinoma of the prostate first diagnosed by BAL highlights the significance of available clinical information and the use of immunocytochemistry for proper diagnosis.