Jeon started her acting career after she joined a management agency and went on her first audition in August 2017, for director
Lee Chang-dong's mystery flick
Burning. An inexperienced actor without any history in the entertainment industry, Jeon won the competition and landed the lead role at her very first audition to play alongside recognized actors like
Yoo Ah-in and
Steven Yeun. Jeon initially did not seek the role of free-spirited Hae-mi in
Burning because she thought she had no chance of getting it. The audition took place only three days after she joined her current talent agency. Director Lee Chang-dong said about her audition, "When I saw her, she seemed to have this very childlike sense of innocence, but at the same time, she carried this sense of duality — as if something much bigger was on the other side of that innocence. So I thought she would be great to give Hae-mi the presence that is so central for the film — conveying that inner depth that this character has." And, "Perhaps I was unconsciously drawn to the fact that everything was a 'first time' for her. Also, she has a face that makes people wonder what she's feeling and thinking. I think that made her a good fit for Haemi's character." Lee also said that although the dance scene was in the screenplay, the dance movements were not planned or rehearsed, but rather Jeon's spontaneous movements. The film received universal acclaim, competing for the
Palme d'Or at the
2018 Cannes Film Festival, and being selected for
The Hollywood Reporter Critics' "15 International Breakout Talents of 2018" feature. Pierce Conran of
Screen Anarchy wrote, "Plucked from auditions, first-timer Jeon Jong-seo achieves something almost unthinkable for a rookie, as she embodies a character who is caught between her dreams and reality, her yearning for freedom and role in society, and the powerful desires of those around her and her own. She is magnetic every time she appears on screen, at once playful and aching with a longing for something that she may never understand."
John Powers of
Vogue wrote, "[i]n a marvelous screen debut, she gives a radiant turn, blooming so brightly—especially in a stoned twilight dance to
Miles Davis—that she often outshines her male costars. Whenever she's not on-screen, the film instantly grows darker, unhappier."
Justin Chang of
Los Angeles Times wrote, "Jeon, making a remarkable screen debut, brings this young woman to beautiful, soulful and defiant life." In 2020, Jeon starred in her second film,
The Call. She played Young-sook, who believes that a telephone connected to the future is the only hope to save herself from making dangerous choices. The film premiered on
Netflix in November 2020. Jeon's performance as the
antagonist in the film was acclaimed. Anthony Kao of
Cinemaescapist called it "an outstanding performance" and wrote, "Jeon's acting gives
The Call a constant current of electrifying suspense that lasts even into its post-credit scenes." James Marsh of
South China Morning Post wrote, "Jun cements her position as Korean cinema's unhinged ingénue du jour, following her star-making turn in Lee Chang-dong's
Burning, with a brilliantly psychotic performance that reveals Young-sook to be just as dangerous as she is fragile and damaged."
Decider's Jade Budowski wrote, "Jong-seo Jun is magnificent as Young-sook [...] She's convincing in both her quieter moments and her more maniacal outbursts, masterfully drawing out all the thrills and chills you could hope for with a movie of this nature". For her performance in
The Call, Jeon won
Best Actress in the
57th Baeksang Arts Awards, and Best Actress awards in the
30th Buil Film Awards and 20th
Director's Cut Awards respectively. The following year, Jeon joined the US-based agency
United Talent Agency under her English name Rachel Jun. She made her English-language film debut alongside
Kate Hudson and
Craig Robinson in
Mona Lisa and the Blood Moon, a fantasy-adventure film by
Iranian-American writer-director
Ana Lily Amirpour, as the lead character Mona. The film had its premiere at the
78th Venice International Film Festival in September 2021. Jeon's performance, as a woman with unusual powers who escapes from a mental asylum and tries to make it on her own in
New Orleans, received positive reviews. Lovia Gyarkye from
The Hollywood Reporter wrote, "Jeon (
Burning) excels in her first English-language role, imbuing Mona with personality despite her limited dialogue".
Variety's Owen Gleiberman wrote, "[i]n Jeon Jong-seo's performance as Mona Lisa, you see the power and the alienation. And the two qualities work together in a cool and empathetic way". She next played a late 20s single woman who swears off relationships in a
romantic comedy film Nothing Serious alongside
Son Suk-ku, directed by Jeong Ga-young of
Hit the Night. Jeon starred in her first series in
Money Heist: Korea – Joint Economic Area, the Korean adaptation of the Spanish
crime-drama Money Heist, as
Tokyo. It was released on Netflix in 2022. She will reunite with
The Call director Lee Chung-hyun for his
short film Ransom alongside
Jin Seon-kyu, and for his Netflix film
Ballerina, in which she portrays a former assassin. On August 22, 2022, Jeon signed an exclusive contract with Andmarq. On March 17, 2024 Jeon threw the
ceremonial first pitch at a preseason exhibition
baseball game in which the
Los Angeles Dodgers played the
Kiwoom Heroes. ==Personal life==