A seemingly healthy 84-year-old female pedestrian was mildly bumped by a car, and she hit her left shoulder, flank, and lower legs when she fell down on a street. She was conscious and stable when transferred to an emergency room. She had no sign of any major injuries except minor lacerations on her legs. Repeated evaluations including chest X-ray, ECG, and focused assessment with sonography for trauma did not reveal any abnormal findings. While waiting for discharge, she started having mild chest discomfort. Unexpectedly, the third echocardiogram showed mild pericardial effusion, and a CT with contrast showed aortic dissection in the ascending aorta and infra-left subclavian aortic dissection. She was immediately transferred by a helicopter to a tertiary trauma center for emergent repair surgery. Considering the site of dissections, progression of existing intrinsic intimal tear triggered by energy impact was suspected. However, traumatic causes could not be excluded. Extra caution and diligence should be exercised when examining elderly patients in blunt trauma.