The emergency services, including the air ambulance, were called to the High Street just before 3.30pm.
A Met Police statement says a man was treated for “a medical episode.”
It’s believed he was treated for an injury to his leg.
Eyewitnesses reported the store was cordoned off and closed.
A London Ambulance Service spokesperson said:
“We were called at 3.02pm yesterday to reports of an injured person in the High Street, New Malden.
“We sent an ambulance crew, two paramedics in fast response cars and an incident response officer to the scene. We also dispatched London’s Air Ambulance.
“The first paramedic arrived in less than four minutes.
“We treated a person for a leg wound and took him to a major trauma centre as a priority.”