In 2007, Sunye made her debut as the leader and main vocalist in the Wonder Girls, a girl group managed by JYP Entertainment, with their single "Irony." On January 26, 2013, JYP Entertainment confirmed that Sunye would stop her official promotions with the Wonder Girls just before marrying James Pak, her Korean-Canadian fiance.
Sunye has contributed her vocals on the tracks of various Korean artists, including Mighty Mouth's "Energy" and Park Jin-young's "Afternoon Separation." She recorded the single "Maybe" for the soundtrack of the popular KBS Korean drama, Dream High. In November 2010, Sunye recorded "This Christmas" with her JYP labelmates as the title track for the debut of JYP Nation with a subsequent music video released on December 1, 2010.
As of December 2014, Sunye released an indirect statement in a report by Joongang Ilbo‘s US branch at a non-profit church concert that she has officially retired from Wonder Girls and the Entertainment industry.
Along with the other Wonder Girls members, Sunye often makes charitable donations to various charities, hospitals, and orphanages around Korea. In September 2010, she made a visit to an elderly man who had secluded himself in the mountains after being a victim to many cases of fraud. According to the producer that followed her, "Sunye prepared clothes, shoes, a radio, food, and various other presents for the man. He hasn’t been able to wash in a while so there was a very bad stench coming from him but Sunye paid no attention to it and held his hands tightly, asking him to live a long life. She also prayed for his good health."
In May 2011, Sunye went on a week-long volunteer mission to Haiti where she cared for children in an orphanage and treated victims of cholera.
Sunye was raised by her grandparents because her mother died when she was very young and her father suffered from a health condition that kept him bedridden. In fall 2007, prior to the Wonder Girls' promotions for their single "Tell Me," Sunye's grandfather died. In October 2009, her father was rushed to the intensive care unit after his condition turned for the worse. She took the first flight from New York, where she resided at the time, to South Korea, skipping out on numerous promotional events to be with her father. On June 23, 2010, Sunye's father died due to a chronic illness he had been suffering from for over 20 years.
During an episode of SBS' "Strong Heart" that aired on November 22, 2011, Sunye announced that she was in a relationship with a Korean-Canadian boy she met in Haiti during a missionary trip. She had kept it a secret until Park Jin-young lifted their "no dating" ban in mid-November. Few details were revealed about him because Sunye admitted that he wasn't a celebrity and is currently living in Toronto, Canada.
On November 26, 2012, JYP Entertainment announced that Sunye was going to marry her boyfriend of two years, James Pak. She got married on January 26, 2013.
On April 4, 2013, Sunye announced through her personal Twitter account that she was expecting her first child with husband, James Pak. She gave birth to her first daughter Hailey (Pak Eun Yoo) on October 16, 2013.