Locking of the metacarpophalangeal (MCP) joint is commonly caused by hyperextension of the thumb or moderate flexion of the index or middle finger. We report a rare case of vertical locking of the MCP joint of the little finger in a 16-year old female after blunt trauma to the little finger. The MCP joint was locked when positioned at approximately 90-degree-flexion and could not extend actively or passively. A manual reduction was easily achieved and no immobilization was applied. Vertical locking of the MCP joint can be easily reduced, and immobilization is unnecessary after reduction. Correct diagnosis prior to reduction and differentiation from other types of locking are essential to prevent overtreatment.