A Hampshire Fire and Rescue Service spokesman said that two applicances had been sent and that crews were seeking to rescue people from a pod near to the top of the wheel at the Clarence Pier fairground.
Reader Susan Kay sent a picture of firemen at the scene, showing them using a hydraulic ladder as they launched the rescue operation.
She said that firefighters were seeking to rescue a woman and child from a pod near the top of the wheel.
Susan, who works at Treasure Island Golf in Southsea, said the fire engines had been at the scene for about 45 minutes.
She said: “They’re bringing a woman and child down, you could see the woman was crying.
“There are loads of people here and everyone’s been stopping to look.”
The woman and child were successfully rescued by lunchtime.
The Solent Wheel, which cost £750,000, was officially opened in March.
It reaches 35m above sea level and has 24 carriages, each seating up to six people.
It is run by the owners of Clarence Pier.