The amphibious pleasure boat burst into flames at midday near Lambeth Bridge, close to the Houses of Parliament, The Times of London reported. Thick smoke could be seen billowing from the bright yellow craft.
The Daily Telegraph reported there were a total of 28 tourists and two crew members on board who were rescued by emergency services and crew members from other boats.
The Telegraph said children as young as 6 were among those who chose to brave the river's waters rather than risk staying on the duck boat.
The Telegraph said three people, including a pregnant woman, were treated for smoke inhalation and others were treated by paramedics for cold and shock.
The Times said a man in his 30s was taken to a hospital to be checked out for a minor head injury.