In early 2011, Hyolyn and group member Bora formed a sub-group Sistar19 with their debut single "Ma Boy". On October 17, she released the single "Ma Boy 2", featuring Electroboyz.
2012-14: First acting role and solo debut with Love & Hate
In 2012, Hyolyn starred in the KBS drama Dream High Season 2 as Nana, a famous idol from the fictional girl group HershE. She was teamed up with Ailee and T-ara's Jiyeon for the song "Superstar" for the drama.
In August 2013, Hyolyn sang an original soundtrack for SBS's drama, Master's Sun, titled "You Make Me Go Crazy". On November 22, Hyolyn shared the stage with Stevie Wonder for a special performance of "I Just Called to Say I Love You" at the 2013 Mnet Asian Music Awards, one of South Korea's biggest music award show. Hyolyn made her solo debut on November 26 with the album Love & Hate. The album consists of double title tracks "Lonely" and "One Way Love", features Korean rappers Mad Clown, Block B's Zico, Dok2, and Geeks's Lil Boi, and some tracks produced by Brave Brothers and Kim Dohoon. On December 31, the music video for the Korean version of "Let It Go" for Disney's animation movie Frozen sung by Hyolyn, was revealed. She became the second Korean singer to participate in a Disney production following Lena Park who previously sang for Disney's "Reflection" for Mulan.
In January 2014, Hyolyn released an OST for the drama My Love from the Star titled "Goodbye". On March 28, Starship Entertainment announced on their Twitter account that Hyolyn would feature in Mad Clown's comeback track, "Without You". The music video for "Without You" was released on April 3. Hyolyn also participated in rapper MC Mong in his comeback to the Korean scene after 5 years with the album Miss Me or Diss Me that was released on November 3. On November 20th, Hyolyn collaborated with singer-songwriter and fellow label mate, Jooyoung, on a project titled "Hyolyn x Jooyoung". Hyolyn was the first idol group singer to participate in the Chuseok special of the singing show I Am a Singer that aired on September 9. The special episode had performances by veteran singers such as The One, Sinawe, Park Ki Young, Kim Jong Seo and Yoon Min Soo. Hyolyn gave two performances and was ranked second place overall in the competition.
Multiple broadcast insiders revealed on January 13, 2015, that Hyolyn agreed to join the lineup of MBC's I Am a Singer Season 3 launch and her agency Starship Entertainment told OSEN that Hyolyn would start filming on the 21st as the first idol singer on the show. On April 2, Hyolyn teamed up with her groupmate Soyou to cover K.Will's latest track "Growing" as Starship Entertainment's cover project. On May 18, Hyolyn along with her fellow Sistar members participated in a collaboration song for KBS's documentary 'I Am Korea' along with EXO, Apink, INFINITE, and many others. On May 21, Hyolyn released an OST for the drama Warm and Cozy called "Closer". On August 17, it was confirmed that Hyolyn will join Unpretty Rapstar Season 2. On August 26, Hyolyn teamed up with Zico and Paloalto for collaboration song "Dark Panda". On September 7, Hyolyn released a free single, "The Wall Destroyer (TWD)" featuring Eluphant's Keebee. Hyolyn released her Unpretty Rapstar's Semi Finals track "My Love" featuring Basick on November 6, 2015. At the end of the show, Hyolyn was placed third. On December 9, it was reported that Hyolyn, Jooyoung, and Bumkey will be collaborating with producing team, Da Internz, for a new song. On December 14, the music video teaser for their collaboration song "Love Line" was released. On December 18, the music video for "Love Line" was released. On December 16, she released an OST for the movie The Little Prince called "Turnaround" along with a music video.
On March 6, 2016, Hyolyn participated in singing competition King of Mask Singer where she was placed in second. The episode included Kwon Seonkook, Youme, Jung Inyoung, Rich, VIXX's Leo, V.O.S's Park Jiheon, and Kang Dongho. On June 17, Hyolyn was a contestant on Duet Song Festival where she and her partner, Lee Nahyun, placed in second singing "Sofa" by R&B singer Crush. The episode had performances from Tei, Eddy Kim, Seventeen's Seungkwan, and Na Yoonkwon. On July 15, Hyolyn released an OST for the KBS2 drama Uncontrollably Fond called "I Miss You".
On October 4, 2016, it was revealed that her first extended play will release soon. On October 11, Starship released a schedule that shows that rapper Dok2 and singer Jay Park will feature in her pre-releases. On October 20, she featured in a song with Far East Movement and Gill Chang titled, "Umbrella". The first single from the album, "Love Like This", featuring Dok2 was released on October 22, along with its music video. The second single from the album, "One Step", featuring Jay Park was released on November 1, along with its music video. Her first extended play It's Me, title single "Paradise", and its music video were released on November 8, 2016.