The objective of this study was to describe the clinical course and response to treatment of five patients who developed loculated pleural effusions as complications of pulmonary thromboembolism (PTE). The clinical charts of five patients who had loculated pleural effusions in the course of their PTE were reviewed, with special attention paid to the duration of symptoms before diagnosis, the pleural fluid analysis findings, and the response of the loculations to anticoagulant therapy. In a tertiary care academic medical center, the five patients described in the present study had multiple locules of pleural fluid seen on chest radiographs and thoracic CT scans. In all cases, the diagnosis of PTE had been delayed for at least 2 weeks after symptoms developed. The loculated pleural fluid had led to the mistaken diagnosis of empyema in three cases. The pleural fluid in all cases was exudative, with a predominance of lymphocytes. With anticoagulant therapy, the loculations largely disappeared within the first few days of therapy. Although most pleural effusions secondary to PTE are relatively small and free-flowing, this study demonstrates that PTE can lead to loculated pleural effusions. The loculations occurred in patients who had been symptomatic from their PTE for > 2 weeks. In each instance, the pleural fluid was a lymphocytic exudate. The effusions rapidly resolved with the institution of anticoagulant therapy. PTE should be included in the differential diagnosis of a loculated pleural effusion, particularly if the pleural fluid contains predominantly lymphocytes.