The patient was a 54-year-old woman undergoing steroid treatment as a maintenance therapy of remission for minimal change nephrotic syndrome (MCNS). After pain appeared in her right-lower abdomen, an abdominal contrast computed tomography scan revealed thrombosis of the right ovarian vein. Laboratory evaluation on admission revealed proteinuria (3.5 g/day) and decreased serum total protein (4.9 g/dL) and albumin (2.4 g/dL) levels, indicating nephrotic syndrome recurrence. Leukocyte and C-reactive protein levels were elevated; over 100 leukocytes/high power field were detected in the urine, and E. coli was detected in both blood and urine cultures, indicating septicemia due to pyelonephritis. The thrombosis disappeared after approximately 27 weeks of heparin and warfarin treatment. The MCNS recurrence was treated with an increased steroid dose; after about 6 weeks, the patient was negative for urinary protein. Her pyelonephritis improved with antibiotic treatment. The patient was discharged in good condition on day 55 after admission. When patients with nephrotic syndrome complain of abdominal pain, venous thrombosis in the abdominal cavity should be considered.