As Kim reached her teenage years, she was cast in more leading roles, notably in the film A Girl at My Door (2014).

Kim played the main character, a nine-year-old girl named Jin-hee, who is abandoned by her father at an orphanage after he remarries, and is later adopted by a French couple.

[10] She played Jung So-mi, the daughter of a heroin addict who is kidnapped by an organized crime ring.

[13] She had her first television role in the drama series Listen to My Heart, playing the younger version of Hwang Jung-eum's character.

[4][14] Kim then had a dual role in the thriller film The Neighbor, playing a murder victim and the serial killer's next target.

[13] Her first role of the year was in the documentary-drama film Manshin: Ten Thousand Spirits, reenacting the teenage version of shamanist Kim Geum-hwa.

[9][17] Her performance was praised by critics—Variety called it "mesmerizing" and Twitch Film noted she had shown more layers and depth compared to her previous roles.

School: Love On as an angel who becomes human, and the thriller film Manhole, playing a hearing impaired girl who is kidnapped by a serial killer.

The two-part drama series is about the "comfort women" in Korea under Japanese rule during World War II, and was later released as a film in theaters.

[26][27] She was cast in her first adult role in the 2016 television drama series, Secret Healer, playing a cursed Joseon-era princess.

[28] Her character has a fictional romance with Heo Jun, played by Yoon Shi-yoon, who is 14 years Kim's senior.

[41] In May 2022, Kim was driving under the influence in Gangnam District, Seoul around 8:00 am; she crashed into several structures including transformers, guard rails and street trees.

In the crash, the transformer broke down, and the electricity supply was cut off for about 3 hours at 57 places including nearby shops, causing damage to merchants.

[42][43] The following day, her agency, Gold Medalist released a statement saying that, "Kim Sae-ron is deeply reflecting on her apparent mistake.

[40] On November 4, 2022, it was reported all the money that Kim had accumulated during her career had been used to cover the costs incurred due to the accident and settlement expenses, and that she had taken a part-time job.