The fresh-faced young man is remarkably upbeat and enthusiastic, especially considering I am meeting him at 10pm at the end of a long day of interviews in a punishing promotional schedule.
He's friendly and down to earth and the exact opposite of a stage school brat. Two years ago he was a regular teenager in a London school when he won the part of Anwar in Channel 4's youth drama Skins.
His mum had seen a newspaper advert for auditions and he almost never went because he was revising for exams, but he did go and his big break had arrived.
"That was great," beams Dev.
"I didn't have a clue what I was doing back then but it was such a cool feeling being on a TV show.
"I was a normal 16-year-old kid living two different lives. I'd go to school and then go and film Skins which then turned into a great show, a real little cult.
"I was glad to be a part of it and I was really learning. It was trial and error – I'd do something and then watch myself cringe and make it better next time."
Just as fate played a part in Dev getting that role in Skins, it also played a part in getting the Jamal role in Slumdog Millionaire.
Director Danny Boyle had failed to find a suitable actor in Mumbai before his daughter – a fan of Skins – pointed him in Dev's direction.
Fate plays a huge part in the plot of Slumdog Millionaire, a classic tale of an underdog overcoming immense odds in his bid to escape from brutal surroundings and find his true love. And it almost sounds like fate was playing a part in Dev's journey to making this film.
"It does," he admits. "It's like there's someone up there looking out for me, and (looks upwards) thank you. I'm such a lucky kid, I don't know what I'd be doing if I wasn't an actor."
The film seems to have touched the hearts of audiences and awards panels everywhere, and I tell Dev it's also turned even hardened critics into weeping romantics.
"That's great," he responds modestly. "I think this film turned me into one as well. I've got loads of Enrique Iglesias and songs like that on my iPod now. I've turned into a soppy little idiot."
The media spotlight on the film will only increase in the run-up to the Oscars and I ask Dev if he feels ready for all of the attention.
Probably not, appears to be the response but I also get the impression he's loving every minute.
He says: "Everything's caught me off guard.
"If you asked me what I would be doing now two years ago, and said I'd have been in a TV show, I'd have said 'no way'.
"If you'd asked me a year ago if I'd have done a film with Danny Boyle, and it's written by the guy who wrote The Full Monty, I'd have laughed in your face. It's surreal. I don't know what's going to happen tomorrow. I've just got to take each day as it comes with a big smile."
With a winning attitude like that, many will be hoping the plucky underdog continues to have a career that looks written in the stars.