Two trains that were on the same track collided just after 1:30 p.m. Wednesday.
According to the Honolulu Emergency Services Department, a 24-year-old woman was seriously injured.
The plantation offers tours aboard the Pineapple Express trains.
A total of five people were hurt, including a 2-month-old who had minor injuries.
Two of the victims were taken to the hospital.
The cause of the collision remains under investigation.