Objective: The spontaneous resolution of vasa previa sonographically diagnosed mid-gestation has been reported. We herein describe a case of the spontaneous resolution of vasa previa and a placental shelf (PS), which were identified at a gestational age of 19 weeks and 4 days. Case description: A 26-year-old pregnant Japanese woman, gravida 4, para 1 (G4, P1), underwent a routine second-trimester fetal ultrasound (US) scan at 19 weeks and 4 days of gestation. Fetal biometry was consistent with the corresponding gestational age, and there was no fetal abnormality. Transvaginal two-dimensional sonography (2D-TVS) showed one small tubular structure and a PS at the periphery of a low-lying posterior placenta. This structure was identified as a small blood vessel in close proximity to the internal cervical ostium (os) on color Doppler. Using pulsed Doppler, this vessel was documented as an artery with arterial blood flow consistent with the fetal heart rate. However, the spontaneous resolution of vasa previa was confirmed 4 weeks later. Conclusion: To the best of our knowledge, this is the first case report of vasa previa and a PS that was diagnosed mid-gestation and spontaneously resolved with advancing gestation. Serial TVS examinations need to be mandatory for cases of mid-gestation vasa previa.