[3][4] Born prematurely, Hyolyn's infancy was complicated by a serious form of biliary atresia, which led to several surgeries, intussuseption and the eventual loss of her gall bladder.

[20][21] In 2012, Hyolyn starred in the KBS drama Dream High Season 2 as Nana, a famous idol from the fictional girl group Hershe.

[29][30][31][32][33] On December 31, the music video for the Korean version of "Let It Go" for Disney's animated film Frozen, sung by Hyolyn, was revealed.

[37] On March 28, Starship Entertainment announced on their Twitter account that Hyolyn would feature in Mad Clown's comeback track, "Without You", released on April 3.

[38][39] She also participated in rapper MC Mong's comeback to the Korean scene after five years with the album Miss Me or Diss Me, released on November 3.

[40] On November 20, she collaborated with singer-songwriter and fellow label mate, Jooyoung, on a track titled "Erase (지워)" featuring Iron, which peaked at number nine on the Gaon Weekly chart.

[46] She was the first contestant eliminated from the show but still impressed viewers with her song choices, especially her emotional rendition of Lee Sun-hee's classic ballad "Fate", which brought the audience to tears.

[56][57] On June 17, Hyolyn was a contestant on Duet Song Festival where she and her partner, Lee Na-hyun, placed second with "Sofa" by R&B singer Crush.

Hyolyn participated in the OST for KBS2' Hwarang: The Poet Warrior Youth with "Our Tears (서로의 눈물이 되어)", released on January 9, 2017.

[68] The track saw success in streaming, digital downloads and, upon its release, hit the upper ranks of several real-time charts including Bugs, Genie and Soribada.

[84] On September 9, 2017, Hyolyn uploaded a handwritten letter to her personal Instagram account, stating that she had decided to leave Starship Entertainment and would start anew without an agency for the time being.

[85][86] In late 2017, Hyolyn featured in two episodes of the music broadcast Fantastic Duo 2, competing against Jinusean and collaborating alongside popular group Got7 with a rendition of her hit track, "Blue Moon".

[99] On April 23, 2018, she revealed the second single from her three-part project, titled "달리 (Dally)", featuring Korean rapper and producer Gray.

[100] For the song's accompanying music video, Hyolyn, along with four other dancers, performed choreography by American choreographer Aliya Janell.

[116] In July 2012, Hyolyn joined Lee Kwang-soo, Kim Jong-kook, and Kang Gary as advertising models for the "Galaxy R Style" edition of the smartphone brand Samsung.

[119] In February 2014, Hyolyn and Yook Joong-wan were chosen as advertising models for Lotte Liquor's 2014 "Like the First" campaign, with a special video released ahead of the promotion.

Hyolyn posted a series of fashion pictorial images with Adidas Originals, featured on with the released of her new single "See Sea" from her three-part project album Set-Up Time.

The brand mentioned tattoos as a key theme, which is emerging as a means of creative self-expression but still has uncomfortable views and misunderstandings.

Hyolyn introduces her experience of getting a tattoo on her abdomen to cover up the scars from her surgery and spread the message of Budweiser's brand spirit of "freedom, challenge, and passion" to the public.

She joined the volunteer organization "Give Love to an Abandoned Dog" in Hwaseong, Gyeonggi Province three years prior to making her debut with Sistar.

Through a feed firm, Hyolyn arranged a fan-signing event that allowed her to contribute enough food for the volunteer group for an entire year.

[138] In February 2014, Hyolyn and Bora took part in a large-scale charity project to commemorate the 11th anniversary of star & fashion magazine InStyle Korea.

Hyolyn and Bora volunteered at Kkongkkongine, a shelter for abandoned dogs under Kara, an animal protection civic organisation in Yongin.

As part of the campaign, photos of Hyolyn and her cat were completed as artworks and sold at an exhibition, the proceeds of which were donated to the animal protection organization Yusaju.