Nigel Marven married Jenny Hull in September 1996, but they separated four years later. Nigel fathered Jane Braham’s son, Theo, but went on to marry Gillian Impey on 1 May 2004. They also have a child. During The Wright Stuff on 14 July 2017 Nigel announced he is currently going through his second divorce. His children are one son Theo and daughter Eleonora.

Marven was born in Barnet but grew up in St. Albans. As a child he loved animals. His first pet was a hamster called Hummy. He kept stick insects, boa constrictors and even an eel in a bath. When he was 15, he also owned young spectacled caiman. Nigel studied botany at the University of Bristol until the age of 22 when he left to begin his career at the BBC Natural History Unit in Bristol. Over the following years, Nigel worked firstly as a wildlife documentary researcher for such programmes as The First Eden and My Family and Other Animals, then went on to produce such series as Realms of the Russian Bear. He enjoyed a 12-year professional collaboration with David Attenborough whom he holds in high esteem. In 1998, he moved to ITV where he was asked to present wildlife documentaries as well as producing them.

In 2000, Nigel became the host of the hit annual Discovery Channel event Shark Week, and held this role for three years. In 2002, the Impossible Pictures production company asked him to present the Walking with Dinosaurs Special episodes “The Giant Claw” and “Land of Giants”, which premiered to nearly seven million viewers in late 2002. In 2003, he also hosted Sea Monsters – A Walking with Dinosaurs Trilogy. He then moved on to Prehistoric Park in 2006, a fictional series about travelling back in time to rescue examples of extinct creatures such as Tyrannosaurus, Woolly Mammoth, Arthropleura and others. In 2009, Marven featured in season 3, episode 4 of the hit action drama series Primeval, where he is seen playing with a baby Velociraptor before encountering a Giganotosaurus, which, it is implied, eats him off-screen. Both Prehistoric Park and Primeval were also made by Impossible Pictures.

Nigel Marven was nominated for BAFTA TV Awards in 2000 for Best Features.

Along with the time-travelling programmes, Marven founded his own independent company Image Impact in 2003, and started producing his own wildlife films, including a few one-hour specials and then series, such as Penguin Safari and Panda Adventure, both which aired on Channel 5 and Animal Planet. In 2007, he also worked with Tigress Productions which resulted in his shows Shark Island and Jaguar Adventure.

In his 2004 nature documentary Bull Shark: World’s Deadliest Shark Nigel Marven was in Bahamas and stood with shark expert Erich Ritter in the water surrounded by sharks. During the filming, a bull shark attacked Ritter’s leg and gave him a 30 centimetre bite to his calf. Marven still recalls it as one of the most dangerous moments in his career.

In 2005, while filming the Indian rhinoceros in Kaziranga National Park, Marven and his crew unknowingly got too close to a female rhino with a small calf; the mother rhino charged at them, but since they were riding in a truck, they were able to outdistance her. Marven later said that this experience was the most exciting moment in his entire film-making career.

Marven was bitten by a venomous green pit viper in East Malaysian state Sabah in the summer 2014 during filming the first episode of the show called Eating Wild. The snake bit him on the thumb but did not inject too much venom, so Marven spent 6 hours in the hospital, until he had recovered. He has also had a few other very dangerous encounters with venomous snakes. While he was producing the BBC film The Serpent’s Embrace in 1980s, a spitting cobra sprayed its venom into his eyes. He spent 2–3 days in hospital, though luckily the venom did not enter his blood. A similar encounter happened in December 2008 while Marven was making a short film about black-necked spitting cobras for Webosaurs. Though he wore a mask, the cobra venom landed in Marven’s hair, then mixed with sweat and ran into his eyes, so he stopped the filming until next morning. In his 2008 series Jaguar Adventure he was bitten by a mildly toxic venomous false water cobra. His hand swelled up within ten minutes, but there were no other harmful effects.

In the third episode of his 2012 series, Wild Colombia, Marven was bitten by a non-venomous Central American tree boa on his nose, causing blood to cover his face. A similar encounter happened in his 2013 show Ten Deadliest Snakes: China with a king ratsnake. Likewise, in Ten Deadliest Snakes: Brazil from 2017, he got bitten on the nose by a non-venomous green vine snake.

One of his more recent successes, Ten Deadliest Snakes, was first broadcast on Animal Planet in the U.S in spring 2014, and on Eden in the UK in June of the same year. Season 2 of Ten Deadliest Snakes premiered in autumn 2015 on Eden, while season 3 began airing on 5 January 2017 on Nat Geo Wild in the UK. Highlights of Ten Deadliest Snakes included, among others, visiting sea krait caves in South China Sea and handling black mamba in South Africa.

During the summer of 2014, Eden Channel in the UK started a new competition for aspiring wildlife filmmakers called Eden Shorts. The task was to make one-minute videos with animals, with the best ones to be shown on TV. Nigel Marven, along with Michaela Strachan, were judges. Nigel has also made some short how-to-guides, available through Eden Channel’s website. In May 2015, Eden premiered a film called Eden Shorts: From Lens to Screen presented by Marven. In the show, he meets competition finalists and reveals techniques used to shoot their videos.

In 2015, he was nominated for Donald Gosling Award by Maritime Media Awards for his series Nigel Marven’s Cruise Ship Adventures.

In 2016, Nigel Marven produced and narrated a short film featuring the work of Black Mamba Anti-Poaching Unit, who are fighting against rhino poaching in South Africa. The film is available to watch via internet and is presented by animal campaigner Anneka Svenska.

In 2016, he received award from Cruise Lines International Association.

In January 2018, Nigel’s Untamed Philippines was screened on Nat Geo Wild in the USA. The presenter-led version of this documentary called Wild Philippines with Nigel Marven aired on Viasat Nature in Europe in March and April 2018 and on Animal Planet India in June 2018, with the American TV channel PBS airing the series in late summer 2019.

As of October 2020, Nigel Marven’s newest series is Wild Central America, a documentary consisting of four episodes, each looking at wildlife of a different Central American country, with focus on Honduras, Costa Rica, Guatemala and Panama. While Wild Honduras premiered on Viasat Nature in summer 2019, the rest of the series aired on the same channel in late spring and summer 2020. The presenter-less version of Wild Costa Rica and Wild Guatemala however, premiered on Nat Geo Wild in February 2020.

In September 2020, Blue Meridian and Crytivo released the official trailer for the video game Prehistoric Kingdom, with Nigel Marven narrating it. On 30 September, the day after the trailer’s release, the creative team behind the game confirmed in a live stream that they had approached Nigel to narrate the trailer after they saw that he followed the game’s official page on Twitter.