Gervasi was educated at Westminster School, and then read modern history at King’s College London. As a teenager in 1981, Gervasi befriended Canadian metal band Anvil when they toured London and became a roadie for the band on three tours, eventually becoming close friends until a falling out in 1986.

Gervasi directed Anvil! The Story of Anvil, a documentary of the Canadian heavy metal band, Anvil, who had then been together for over 30 years. Gervasi first met Anvil on 21 September 1982, after a gig at The Marquee Club in London. He introduced himself to the band as “England’s number one Anvil fan”. He subsequently became a roadie for the band on their 1982, 1984 and 1985 tours, and was given the nickname “teabag” by the band. He reunited with Anvil after a break of 20 years, and started filming a documentary about them in November 2005.

Gervasi’s first position was to work for the Poet Laureate of the United Kingdom, Ted Hughes at the Arvon Writing Foundation. After completing his degree, he subsequently worked for John Calder of the Samuel Beckett archive helping to arrange a vast sale of Beckett’s personal papers at Sotheby’s in 1989, including Beckett’s own annotated version of Waiting for Godot which sold to Trinity College, Dublin.

In August 1993, Gervasi, then a young journalist working for the Mail on Sunday, was sent to Los Angeles to interview a number of high-profile celebrities, as well as Hervé Villechaize, the diminutive French actor who starred as Tattoo on the hit American TV series Fantasy Island and as Nick Nack in The Man with the Golden Gun. In October 2018, Vulture published a first-person account of his experiences with Villechaize.

Twenty-five years after meeting Villechaize, Gervasi wrote and directed My Dinner with Hervé, a biopic of the actor based on the interviews conducted only days before the actor committed suicide in 1993. The film stars Emmy Award- and Golden Globe-winning actor Peter Dinklage and was produced by Oscar-winning Schindler’s List writer Steven Zaillian. The movie aired on HBO and has been nominated for an Emmy Award, Critics’ Choice Award, PGA Award, and WGA Award for Best Longform Original. The film holds an 83% positive on Rotten Tomatoes.

Gervasi moved to Los Angeles in 1995 to attend the graduate screen-writing programme at UCLA Film School, where he twice won the BAFTA/LA scholarship. While in the programme, he supported himself by working as a journalist, writing for newspapers and magazines, including The Sunday Times, The Observer, and Punch.

From 1999 to 2000, he was the voice of Jaguar Cars on US radio and television.

Gervasi got his film-writing start with The Big Tease, which he co-wrote with Craig Ferguson. He went on to pen The Terminal, made into a film in 2004 directed by Steven Spielberg. According to London’s The Daily Telegraph: “He is one of only two English screenwriters to have their scripts made into movies by Steven Spielberg. The other is Tom Stoppard [for Empire of the Sun].”

On 14 May 2006, Geri Halliwell gave birth to their daughter, Bluebell Madonna Halliwell.

The film premièred at the Sundance Film Festival in January 2008, and won Audience Awards at the 2008 Sydney Film Festival, Los Angeles Film Festival and Galway International Film Festival.

He was appointed the Hunter/Zakin screenwriting chair at UCLA and taught there in spring 2009.

In 2009, Gervasi presented Steven Zaillian with the Austin Film Festival’s Distinguished Screenwriter Award.

In 2009, the Motion Picture Association of America opened the category of Best Picture nominees from 5 to 10. In October 2009, Anvil! The Story of Anvil was the first screener to be sent out for considering of the expanded Best Picture category as well as for Best Documentary. There was disappointment when Anvil was one of the higher-profile films not short-listed in the Best Documentary category.

Other films for which he has written include Comrade Rockstar and How to Marry a Millionaire. He wrote and executive produced Henry’s Crime. The film debuted at the Toronto Film Festival in September 2010.

Anvil! The Story of Anvil won an Emmy Award in 2010 in the category of Outstanding Arts and Cultural Programming.

In 2010, Gervasi married British theatre producer Jessica de Rothschild, daughter of British financier Evelyn Robert de Rothschild.

In 2012, Gervasi directed Hitchcock starring Anthony Hopkins as Alfred Hitchcock, Helen Mirren as his wife Alma, and Scarlett Johansson as Janet Leigh.

In September 2018, The Guardian ranked Anvil! as the 7th best music documentary of all time. In NME’s survey of ’50 Awesome Music Movies’, Anvil! is ranked number 2. A 2017 New York Post Decider article on the movie said, “almost ten years on from its initial release, Anvil ranks up there with the best rock documentaries ever made.”

In November 2018, Mark Povinelli, the president of Little People of America, published an article on Variety stating that the film’s depiction of Villechaize was an important step for the representation of little people.