Born and raised in Camden Town, North London, Contostavlos grew up with his parents, Byron Contostavlos and Zoi Agorou and older brother Spiros. His father had been a member of the group Mungo Jerry. Byron died on 12 April 2007. He is of Greek-Cypriot descent.
When Contostavlos was younger, he attended Richard Cobden Primary school, then St Aloysius secondary, a Roman Catholic boys-only school in Islington, attending for a year before being expelled for truancy. In N-Dubz's book Against All Odds: From Street Life to Chart Life, Dappy says that he doesn't remember the school "because I wasn't there often". He then attended Bishop Douglass School when he was around twelve years old, where he got into fights "almost everyday", which "...always started if someone had been making fun of me or something stupid".
Dappy eventually dropped out of education when he was 15, but he returned later to study at college and received an A* in English and a B in GCSE Music.
However, realising they shared so much in common, Dappy and Fazer (who he had first met at karate lessons when he was 9, before becoming best friends with him at school) started making beats together and coming up with lyrics, later asking Dappy's cousin, Tulisa (who was reluctant at first), to join the band and started to perform in and around Camden Town from the age of thirteen. At the time they were called the Lickle Rinsers Crew and went under the management of Dappy's father Byron, who to Dappy was the "inspiration behind the band". Byron worked at a local barbers shop, putting all the money he had into equipment and resources for the band at their studio. However, Byron died on 12 April 2007 after a heart attack and N-Dubz wrote the song "Papa (Can You Hear Me?)", which was played at his funeral and became the group's second biggest hit at #19, and at #17 in the download charts. Dappy later described his dad's death as "the lowest point in our lives, we had no money, no manager, no driver, no accountant, but most of all I had no father—B was everything to me and it hurts so much to think that he never got to see what we have achieved now, but I know he's looking down on us and he'd be really proud".
Dappy had the words "RIP Dad" tattooed on his neck and doesn't like to say his dad's name, instead referring to him as "B" or "Uncle B", which was also the name of N-Dubz's debut album. Before Byron died, he said he'd like their album to be called Against All Odds but, after his death, the group called their debut album Uncle B in tribute, with their second album being called Against All Odds.
Dappy appeared on the television show Never Mind the Buzzcocks on 29 November 2007, on Phill Jupitus' team, and wore a trademark "Dappy hat", also giving one to Simon Amstell to wear as part of the gag. Despite vowing he would not return to the show he appeared for a second time on the guest team on 4 December 2008 and for a third time, on Phill's team, which was broadcast on 18 November 2009. He is known to be a good friend of Chris Moyles and also gets on well with Tinchy Stryder after releasing a single together, called "Number 1", although in the past they have said to have fallen out many times over credits for the song. They responded by telling the crowd after their performance at BBC Radio 1's Big Weekend in May 2009, "and remember, don't believe what the media say 'cos it ain't true". Dappy has made cameo appearances on K.I.G's "Head, Shoulders, Kneez and Toez" music video, Gracious K's "Migraine Skank" music video, and Chipmunk's "Chip Diddy Chip" music video, as one of Chipmunk's school friends.
It was announced on 17 June 2011 that N-Dubz had left their American record deal, amid rumours that the band had split. These rumours began circulating again in August 2011; however, Dappy insisted the band had not split, but were simply taking a break. As such, during the band's hiatus period, all three members decided to embark upon solo careers. Before the band's split, Dappy signed a contract with Takeover Entertainment Ltd that confirmed that if the band ever split or went on hiatus, he would continue as a solo artist. His first taste of solo stardom came as a guest artist on label-mate Tinchy Stryder's single "Spaceship", which was released in June 2011. While deciding upon his debut solo single, Dappy was contacted by Def Jam, asking him what he would like done with the demos of a track N-Dubz had recorded whilst under the label, which remained unreleased. Dappy decided to re-record the track, "No Regrets", and release it as his debut solo effort. Featuring a cameo appearance from band-mate Fazer, "No Regrets" took the charts by storm, peaking at #1 in the UK and Scotland, and at #8 in Ireland.
Following the success of "No Regrets", Dappy claimed during an interview that: "With my solo stuff, I really want to earn the respect of an older audience. I don't think there's any shame in trying to write music that will be recognised by people I admire. Bono. I have big goals. I want to have two #1 singles back-to-back as a solo artist." Dappy soon succeeded, gaining praise from Queen guitarist Brian May, who was "impressed" with "No Regrets". As a result, Dappy invited May for a guest stint on his second single, which co-incidentally was titled "Rockstar". "Rockstar" was released on 26 February 2012. On 29 February, Dappy revealed that the title of his album would be Bad Intentions, claiming that the album "is motivational music for people who believe they can't do nothing, a battle we have with our own mind." The album's third single was "Come with Me". Subsequently, he revealed that the fourth single will be "Good Intentions", and if "Rockstar" peaks at #1 on the UK Singles Chart, he will enlist Barbadian singer Rihanna and British superstar Adele, who will both have vocal sections on the single. He claimed that Rihanna contacted him after she was impressed with a demo tape she had heard of his music. Dappy confirmed in September 2011, before the release of "Rockstar" and "Bad Intentions", that the album's final single will be a collaboration with The Wanted, which will be released towards the end of 2012.