2015: SIXTEEN, debut with TWICE, and controversy
On May 5, 2015, she became a contestant on JYP's newest survival show, SIXTEEN. Unfortunately, in the final episode, she didn't made it to the final line-up. However, based on a unanimous decision, JYP, along with the trainers and the A&R team, brought her back and included her in the group. They officially debuted on October 20, 2015 with their first mini album, The Story Begins.
Controversy arose as fans became skeptical of the motivations behind the decision of the addition of Tzuyu and previously eliminated Momo. Tzuyu was a fan favorite throughout the series and JYP included her due to her popularity and star quality.
The following day after the final episode, JYPE released a short statement about the addition of the two girls into the final lineup of the group: "We apologize for failing to clearly communicate the selection process, and we'd like to explain it in detail once again. The condition to be chosen as a final member was the votes made by the audience and viewers. However, leading up to the final episode, we thought that the seven members selected officially may leave something to be desired. So, in addition to the seven, we decided that one member would be added solely from viewer's opinions (Tzuyu) and one from solely Park Jin Young's opinion (Momo)."
2015–2016: Flag incident
On November 28, 2015, Tzuyu, along with her non-Korean fellow members from TWICE appeared on the internet variety show My Little Television. During the program, Tzuyu held up a Taiwanese flag to show her nationality. Member Mina, Sana, and Momo did the same for their country, Japan. However, Tzuyu's action was picked up by the Taiwanese singer China-based Huang An, who opposes Taiwanese independence from China, and described Tzuyu on his Weibo account as a Taiwanese independence supporter. In response to the controversy, JYP China stated on their official Weibo account that, until the misunderstanding have been resolved, TWICE's activities in China would be halted.
As an apology, a video of Tzuyu was released on JYPE's channel on January 15, 2016. In the video, she is seen standing in front of a gray wall, facing the camera in a casual attire. Speaking Chinese, she begins with a short self introduction, followed by "I'm sorry", and continuously saying how proud she is about being Chinese. The video had a very polemical YouTube rating, alongside the general public stirring backlash against the video. Many political figures in Taiwan, including presidential candidates and the outgoing president, released statements supporting Tzuyu.
Huang An was given backlash of his own, while JYP Entertainment's website suffered a DDoS attack. Both Huang An and JYP Entertainment were faced with subsequent legal threats over the flag incident.
- SIXTEEN (Mnet, 2015) - contestant
Music video appearances
- GOT7 - "A" (2014)
- GOT7 - "Stop Stop It" (2014)
- miss A - "Only You" (2015)
- J.Y. Park - "Fire" (feat. Conan O'Brien, Steven Yeun, & Jimin Park) (2016)
- Yes, I Am Tzuyu... (2020)
- She has a dog named Gucci.
- She is good friends with Elkie and Shuhua.
- She attended Hanlim Multi School with Chaeyoung.
- In Gallup Korea's annual music polls which interview 1,500 people between the ages 13–29, Tzuyu was voted the 3rd most popular idol in 2016, the 9th in 2017, and the 12th in 2018. In the poll's history, she is the most popular non-Korean idol.
- She was nominated for "The 100 Most Beautiful Faces of 2020".
- She ranked 1st place in 2019.
- Her MBTI Personality is ISFP-A (adventurer) 
- Main article: Tzuyu/Gallery
- (KR) Hankyung: '정치색 논란' 트와이스 쯔위 "한국식 이름 마음에 든다"…뭐길래?
- (KR) Nate: '식스틴' JYP의 미래 짊어질 9인, 걸그룹 트와이스 탄생 (종합)
- Soompi: JYP Addresses Controversy Surrounding Final Lineup of TWICE
- (KR) Naver: JYP "'식스틴' 트와이스 선발 과정, 충분히 소통 못해 죄송"(전문)
- Soompi: TWICE Halts Chinese Activities in Light of Nationality Controversy Surrounding Member Tzuyu
- Soompi: TWICE's Tzuyu Personally Apologizes for Nationality Controversy
- The Straits Times: Video of K-pop Singer Chou Tzu-yu Apologising for Waving Flag Angers Taiwanese on Polling Day
- Focus Taiwan: Timeline of The Chou Tzu-yu Flag Controversy
- BBC News: S Korea Website 'Hacked' Over Chou Tzuyu Taiwan Flag Row
- Korea Joongang Daily: Criticism Narrows in on JYP, Park
- Soompi: CLC's Elkie Wishes TWICE's Tzuyu A Happy Birthday With A Lovely Message
- Soompi: (G)I-DLE’s Shuhua Celebrates Birthday With TWICE’s Tzuyu And CLC’s Elkie
- Soompi: Idols Graduate From Hanlim Arts School And Lila Art High School
- Soompi: Koreans Choose Top 10 Artists And Top 20 Idols Of 2016
- Soompi: Koreans Choose Top Singers, Songs, And Idols Of 2017
- Soompi: Koreans Vote For Artists Who Shined The Most + Favorite Songs And Idols Of 2018
- @tccandler on Instagram (April 10, 2020)
- @tccandler on Instagram (December 29, 2019)
- Finding TWICE's MBTI EP. TZUYU