Images posted on social media show the train remained upright but came off the tracks and stopped just short of hitting a station building.
The driver of the train left suffering from "shock", the Mayor of London said.
Sadiq Khan told ITV: “Thankfully there aren't the kind of casualties that we could've had. There will be a full inquiry to get to the bottom of this."
A resident who was due to catch the train that crashed at Enfield Town station said he’s “never seen anything like it before”.
Enrolment assistant Kyel Matin told the PA news agency that he was supposed to be on the 08.24 train to Liverpool Street, but showed up to “crowds of school kids and commuters waiting outside”.
“(It was) pretty chaotic. Commuters and kids (were) rushing in, all wanting to get a good photo,” the 31-year-old said.
Ruth McBryan, 40, who works in offender rehabilitation and was due to catch the same train, told PA: “I saw big crowds and everyone was confused.”
“I was in a train crash as a child but it didn’t bring back any bad memories.”
Gary Spencer, a worker at a sorting office, said there were dozens of emergency vehicles outside the station but the situation seemed “very much in control”.
"(There was) initially some shock but more importantly (I was hoping) that there were no casualties," he said.
"I have never known a train to fail stopping at the end of the line... if the metal steel was not behind the buffer I'm confident the train would have damaged the building.
"The situation seemed very much in control."
Ellie Burrows, Network Rail's route director for Anglia, said: "At approximately 8.20am a train hit the buffer stops at Enfield Town at slow speed.
"The driver is being treated for shock and there are reports of a few minor injuries.
"Emergency services including the British Transport Police are on site and an investigation is under way."
Rory O’Neill, TfL’s General Manager for London Overground, said: “A London Overground train had a low speed collision with a buffer at around 8.20 this morning at Enfield Town station.
“Emergency services attended this morning and there will be a full investigation to establish how this happened.”
A London Fire Brigade spokesman said: “An eight carriage passenger train derailed after hitting buffers at the station.
“Around 50 people were evacuated from the train before the Brigade arrived by TfL and station staff. Two people have been treated at the scene for minor injuries by London Ambulance Service crews.
“The Brigade was called at 8.27am and is still at the scene. Three fire engines and two fire rescue units are in attendance.”
Station Commander Jim O’Neill, who is at the scene, said: “The train has hit the buffers at the station, which is at the end of the line, and gone up over the top of them.
“Firefighters carried out a systematic search of the train to ensure there were no further people on board.
“Crews are now assisting station staff to make the scene safe and a recovery operation.”
A London Ambulance Service spokeswoman said: “We were called at 8.16am this morning to reports of a train derailed at Enfield Town railway station, Enfield.
“Two people were assessed at the scene for minor injuries, but they were not taken to hospital.”
There’s still no London Overground service between Enfield Town and Edmonton Green.
National Rail tweeted: “An operating incident at Enfield Town means no trains will run between Edmonton Green and Enfield Town.
“Trains will continue to run as normal between London Liverpool Street and Edmonton Green before diverting to Cheshunt. We expect this to continue until approximately 3pm.”