Thrombosis of the left renal vein (LRV) is a rare occurrence usually associated with hypercoagulable disorders. It may also be caused by extrinsic compression due to anatomical variations. Such variations, known as nutcracker phenomenon (NP), are usually completely asymptomatic, and they have been described in three variants: a narrowed aortomesenteric angle (AMA) with entrapment of the LRV; a second, rarer variant with an anomalous retro aortic LRV compressed between the abdominal aorta (AA) and the spine (posterior nutcracker syndrome, PNCS); and a third variant with a duplicated LRV with a pre- and retroaortic course, compressed both anteriorly and posteriorly. The development of symptoms secondary to NP is mainly due to renal congestion, often difficult to identify, and includes flank pain, ipsilateral varicocele, hematuria, and orthostatic proteinuria, among others. The most severe complication of NCS is LRV thrombosis with or without associated predisposing prothrombotic factors. The present case associates a PNCS to LRV thrombosis with a floating thrombus in the inferior vena cava and pulmonary embolism.