In 2015, Jarvis auditioned and was cast to portray the character of Sebastian in William Oldroyd's debut feature film
Lady Macbeth. Jarvis has starred in two stage plays directed by
Richard Jones, the 2017 production of
The Hairy Ape by
Eugene O'Neill at
Park Avenue Armory in New York and
The Twilight Zone at the
Almeida Theatre in London. In 2019, his portrayal of Arm in the independent film
Calm with Horses earned him a nomination as
Best Actor at the
British Independent Film Awards 2020 and
London Film Critics' Circle. Adapted from the short story of the same name from the collection
Young Skins by Colin Barrett,
Calm with Horses was received positively, with critics praising both Nick Rowland's work as a debut director and Jarvis' performance as Douglas Armstrong. The film was released in the United States under the title
The Shadow of Violence. In 2020, Jarvis was a guest star on the fifth season of
Peaky Blinders, as the character Barney. Following
Peaky Blinders, Jarvis appeared in
Nocturnal,
Funny Face,
The Evening Hour and
Raised by Wolves. In 2021, Jarvis was announced to star opposite
Dakota Johnson in
Netflix's adaptation of
Jane Austen's
Persuasion. He was also cast as
John Blackthorne, a leading role opposite
Hiroyuki Sanada in
FX's 2024 limited-series
Shōgun, the
second TV adaptation of
James Clavell's best-selling
novel of the same name. In 2022, Jarvis was nominated for
Best Lead Performance in the
British Independent Film Awards' new gender-neutral category for his performance in
It Is In Us All. He was also nominated for
Best International Actor at the
Irish Film and Television Awards.
FX's
Shōgun premiered in February 2024, receiving critical acclaim worldwide. Jarvis' performance as John Blackthorne was described as a "force to be reckoned with" by
IGN and
The Washington Post wrote that he "brilliantly channels" his role as the marooned English pilot in the historical drama.
Empire described Jarvis as "compelling" and "magnetic". In his review, Nick Clark wrote for the
Evening Standard, "Jarvis is one of those actors who is not just chameleonic – anyone who has seen him in
Calm with Horses and then
Persuasion can attest to his powers of transformation – but always brings so much more to a role than just speaking the words in order. It's the eyes; there's a whole lot going on behind them, and it means he's never less than compelling." In 2025, Jarvis starred in the Australian prison drama
Inside,
The Alto Knights, starring alongside
Robert De Niro and directed by
Barry Levinson, and Ray Mendoza and
Alex Garland's
Warfare. Jarvis' performance in
Warfare as Navy SEAL veteran Elliot Miller was widely acclaimed by critics, with Aiden Kelly writing "Every actor does a fantastic job, particularly Cosmo Jarvis in a part that once again shows the rising newcomer’s incredible range." for
Collider. In January 2025, Jarvis joined the cast of
Guy Ritchie's
Wife & Dog. In March 2025, Jarvis joined the cast of
Christopher Nolan's
The Odyssey, although he would drop out shortly before filming commenced due to scheduling conflict . In April 2025, Jarvis was officially confirmed to return as John Blackthorne for the second season of
Shōgun alongside
Hiroyuki Sanada. In May 2025, Jarvis was announced to star as future Soviet leader
Joseph Stalin in
Young Stalin, a film based on the biography of the same name by historian
Simon Sebag Montefiore. In October 2025, Jarvis joined
Paul Greengrass'
The Uprising (formerly titled
The Rage) led by
Andrew Garfield, an action period drama film set in during the
Peasant's Revolt. ==Personal life==