In 2015, Taeyeon released her debut extended play (EP) I, whose titular single reached number one on South Korea's Gaon Digital Chart.

In 2016, she released the number-one single "Rain" as part of the SM Station project, followed by her second EP Why, which peaked atop the Gaon Album Chart.

Additionally, Taeyeon has recorded soundtracks for various television dramas and films, including "If" for Hong Gil-dong (2008), "Can You Hear Me" for Beethoven Virus (2008),[1] and the chart-topping "All About You" for Hotel del Luna (2019).

[26] Following a radio hosting job in 2009–10,[27] Taeyeon journeyed into acting, making her theatrical debut in a lead role in the 2010 musical A Song to the Sun.

[31] Despite the favorable response, Taeyeon later described musicals as difficult, stating that her weak concentration made it hard for her to act and sing at the same time.

[50][51] In January 2013, Taeyeon and Tiffany sang a duet, "Lost in Love", which was featured on Girls' Generation's fourth Korean album, I Got a Boy.

[58] Her other releases in 2014 included "Colorful" for JTBC's campaign "The World Is More Beautiful Because We're Different" and "Love, That One Word" for the SBS's drama You're All Surrounded; the latter entered Top 10 on both Gaon Digital Chart and K-Pop Hot 100.

[61][62][63] In February 2015, Taeyeon accepted a personal request from f(x)'s Amber to feature in "Shake that Brass", the lead single from her debut album, Beautiful.

[69] The commercial success of I, according to Yonhap News Agency, was the main contributor to SM Entertainment's leading music sales in the fourth quarter of 2015.

[70] The title track, which features rapper Verbal Jint, incorporated elements of pop rock that marked a departure from the ballad sound she had been known for until then.

[76] Taeyeon featured on Yim Jae-beom's "Scars Deeper than Love" (2015),[77] Verbal Jint's "If The World Was a Perfect Place" (2015),[78] and Crush's "Don't Forget" (2016).

[84] She also became a spokesperson for Sword and Magic, a game developed by the company Longtu Korea, for which she recorded a rendition of BoA's 2003 song "Atlantis Princess".

[108][109] Hong Dam-young of The Korea Herald highlighted Taeyeon's "calm and undeniable vocal prowess" in the album while praising the songs as "the most sophisticated Christmas tunes" of the year.

[115] That same month, Taeyeon embarked on a Japan Showcase Tour, available only to members of SM Entertainment's official Japanese fan club.

[117] That same month, Taeyeon was announced to be part of Girls' Generation's second subgroup, Oh!GG, which consisted of the five members that re-signed with SM Entertainment; the group released their first single, "Lil' Touch" in September.

[131][132] She also recorded "All About You" for the TVN television drama Hotel Del Luna; the song topped the Gaon Digital Chart for two consecutive weeks.

[177] On August 29, Taeyeon collaborated with British musician Sam Smith to release a Korean duet version of "I'm Not the Only One", as part of the reissue project of their debut studio album, In the Lonely Hour 10 Year Anniversary Edition.

[178][179] On October 27, it was announced that Taeyeon would be releasing her sixth extended play Letter to Myself on November 18, containing six tracks including the lead single of the same name.

In 2009, on MBC's Yoo Jae-suk & Kim Won-hee's Come to Play, Park Jin-young of JYP Entertainment expressed his wish to work with Taeyeon because of her "ability to tell a story through singing.

"[187] Music producer Jo Young-soo, who wrote her song "Like a Star", was likewise impressed by Taeyeon's ability to convey a variety emotions through her vocal performance.

Seo Geun-young, a faculty member in the Postmodern Music Department at Kyung Hee University, highlighted Taeyeon as a vocalist who excels in maintaining the intricate balance between the thyroarytenoid and cricothyroid muscles while showcasing clarity in both low and high vocal ranges.

Oh Han-seung, head of the Vocal Department at Dong-ah Institute of Media and Arts, highlighted Taeyeon's distinctive presence, emphasizing her ability to make the songs stand out without relying on elaborate arrangements or strong beats.

[204] She has influenced numerous K-pop artists, including Lovelyz's Jiae,[205] Melody Day's Chahee,[206] Cosmic Girls' Luda,[207] CLC's Elkie,[208] Sonamoo's High.D,[209] Baek A-yeon,[210] Mamamoo's Moonbyul,[211] and Heize.

[213] In July 2019, Taeyeon donated ₩100 million to the Korean Red Cross, to help for support women, children and teenagers from low-income families in her hometown in North Jeolla.

[215] The Red Cross Society of North Jeolla Province planned to expand its support for health supplies for women, girls and adolescents by recommending three primary, middle, and high schools in the region as beneficiaries of Taeyeon's donation.

[221] In 2016, when Taeyeon's contract with Nature Republic expired, the cosmetic brand Banila Co. selected her to be its new spokesmodel due to her domestic and international popularity.

[222] In March 2019, Taeyeon represented the Chanel's Rouge Coco Flash Lipstick collection through beauty pictorial in the April issue of Elle Korea.

"[225] In August 2021, she was selected as ambassador for South Korean super-premium skincare beauty brand Sulwhasoo's "New Concentrated Ginseng Renewing EX" campaign.

She featured in commercial films for the product, broadcasting in various mass media channels, including numerous Thai local television and radio stations.

Since debuting as a member of Girls' Generation, Taeyeon has received numerous nominations and awards for her solo activities in original soundtracks, radio show hosting and musical theatre.