BACKGROUND Urine pregnancy tests are usually performed by women at home and also by healthcare professionals. However, there are several conditions that may cause a false-positive urine pregnancy test, including trophoblast tumors, malignancy, nephrotic syndrome, adenomyosis, tubo-ovarian abscess, and paraneoplastic syndromes. A case is presented of a false-positive urine pregnancy test in a 28-year-old woman with a history of tubal ligation, who had a delayed diagnosis of obstructive pyelonephritis due to renal calculus. CASE REPORT A 28-year-old woman had previously been sterilized by tubal ligation. She presented with acute pyelonephritis associated with a left staghorn renal calculus and was found to have a false-positive urine pregnancy test, which delayed the diagnosis and management of her acute pyelonephritis. On follow-up, she had a negative serum pregnancy test. Abdominal computed tomography (CT) identified a left-sided staghorn calculus resulting in partial ureteric obstruction and hydronephrosis. She was treated with antibiotics, including cefazoline, and a left nephrostomy tube was sited to treat her hydronephrosis. Her pain was initially managed with acetaminophen and hydrocodone. Four days after her initial hospital admission, the patient was stable enough to go home on oral levofloxacin and pain medication. CONCLUSIONS This case of a false-positive urine pregnancy test in a 28-year-old woman with a history of tubal ligation highlights that this association may result in the delay in the diagnosis and treatment of acute pyelonephritis.