Police said officers attended the incident, at a construction site on Kirkhaw Lane, with the ambulance service just before 11.10am.
A spokesman said the force received a report that a man in his 30s had suffered a leg injury.
He was taken to Pinderfields Hospital for treatment.
Wakefield District Patrol Team 5 said on Twitter that a girder had fallen, but no one was badly injured.
The Express understands the Health and Safety Executive has been made aware of the incident and has contacted the organisation for comment.