Polyarteritis nodosa (PAN) is characterized by medium- or small-sized artery vasculitis with vessel wall inflammation and necrosis of muscular arteries, commonly presenting with fatigue, fever, weight loss, and joint pain. PAN in pregnancy is rare and is associated with worsening of vasculitis after delivery, resulting in myocardial infarction and heart failure which frequently lead to maternal death. We report a case of hypertensive disorders of pregnancy (HDP), which is difficult to differentiate from PAN. A 27-year-old multigravida was diagnosed with PAN 4 years prior after experiencing fever and lower extremity skin rash. During her PAN remission, she conceived her second pregnancy and opted to discontinue PAN medication and declined antihypertensive medications. At 22 weeks of gestation, her blood pressure was elevated to 200/100 mm Hg without proteinuria, for which she was admitted to our hospital. She was diagnosed with HDP-chronic hypertension without PAN recurrence due to the absence of PAN-specific skin or joint symptoms according to the PAN diagnostic criteria. Antihypertensive medication was administered. At 30 weeks of gestation, her blood pressure was poorly controlled and she developed proteinuria, which led to a diagnosis of superimposed preeclampsia that necessitated emergency cesarean section delivery. After delivery, her blood pressure was immediately controlled using antihypertensive medication. Our case report highlights the importance of carefully managing HPD as a serious complication of PAN.