A 24-year-old, 19-week pregnant female presented to a community hospital emergency department following an acute hyperextension injury to the left wrist. The pertinent findings on the initial examination included pain, swelling of the ulnar aspect of her palm, and decreased, painful flexion of her small finger. The emergency room physician suspected a flexor tendon injury, and urgent referral to a tertiary level plastic surgery center was made. After plastic surgery evaluation, it was determined that her symptoms were related to the ulnar nerve opposed to an acute tendon injury. After ruling out common surgical pathologies, the diagnosis of palmaris brevis syndrome was provided. Palmaris brevis syndrome does not typically present acutely or post-trauma, and thus is not commonly observed by emergency physicians or acute care hand surgeons. This atypical presentation highlights that palmaris brevis syndrome should be considered in the differential diagnosis of new onset ulnar-sided hand pain.