He added: 'My wife Yari and I were going to Canary Wharf and saw a boat in the middle of the river with smoke billowing from the back.
'We thought it was going to park up at the pier but it overshot it and I thought "this isn't going to end well".
'We heard that there was a fire in the engine room and it was quite alarming to see.
'There were a lot of people on board and they looked like they were celebrating an event.
'We heard babies crying on board and I was concerned about the fire and my wife phoned the police straight away.
'We saw a police helicopter and a number of ambulances arrived on the scene, luckily no one was seriously hurt.'
Police said emergency services were called to reports of a boat on fire shortly before 4pm.
A Metropolitan Police spokesman said: 'We were called at 4.20pm to reports of a fire on board a boat near Canary Wharf Pier.
'The boat was evacuated and all of those on board were brought to shore. There were no reports of any significant injuries.'
A Port of London Authority spokesman confirmed that both of the boat's engines had failed as a result of the fire and added that no one was injured in the crash.
Some 142 passengers and six crew were evacuated from the vessel, while three other staff members remained on board.
A London Fire Brigade spokesman said: 'Firefighters and officers were called to a small engine fire on a tour boat in the Thames this afternoon.
'The fire was extinguished before the Brigade arrived.
'142 passengers and six crew disembarked to two other boats that were nearby and there are no reports of any injuries.
'Crews checked the boat for safety and ensured that the fire was out.
'Eight fire engines and the fireboat attended the incident from stations including New Cross, Greenwich, Millwall and Shadwell.
'The Brigade was called at 3.41pm and the incident was over for the Brigade at 4.26pm.'