Yoseob was born in Seoul, South Korea on 5 January 1990 in a small family with one older sister. He first gained interest in music and started practicing singing after listening to Brian McKnight's music. He then listened to a lot of music of a similar style, but he realized that he couldn't be biased towards a certain genre and started listening to dance music and rock as well. When he was in high school, he joined a school band where he performed a lot of hard rock and metal during their performances. Yoseob actually wanted to try modern rock; however, his seniors at that time said that it would ruin the mood and ultimately not be a success.
Yoseob became a JYP Entertainment trainee, but left after receiving a bad grade from practice reviews. He moved agencies, to M Boat Entertainment (a former sister company of YG Entertainment) where he was trained for 5 years before transferring to Cube Entertainment where he finally became a member of Beast. While still a trainee at Cube Entertainment, he became a backup dancer for AJ, his soon-to-be group member and former high school friend, now known as Lee Gi Kwang, in the music videos and live performances of "Wiping the Tears" and "Dancing Shoes".
Yoseob is the main vocalist of Beast. He released a digital single together with Dalmatian’s Daniel titled “First Snow and First Kiss”  and participated in singing original sound tracks (OSTs) for various Korean dramas such as “Happy Birthday” for More Charming by the Day and “I Cherish That Person” for My Princess. and "Loving You" – for All My Love. Yoseob has also participated in various TV shows, including KBS's "Oh! My School".
Yang Yoseob attended Dong-ah Institute of Media and Arts (formerly known as Dong-Ah Broadcasting College) and has graduated in 2014.
Along with fellow Beast member Jun Hyung, MC Lee Hyukjae, Moon Hee Jun (formerly of H.O.T.) and Kim Sook, Yang welcomed Japanese tourists for the "Visit Seoul 2010" campaign, where Korean celebrities and Japanese tourists explored Seoul through MBC's Star Guide Doshiraku to boost visibility of Seoul's famous landmarks and cuisine. On July 16, 2010, Yang participated in the official soundtrack of the Korean drama More Charming By The Day as part of its promotional campaign, with the song "Happy Birthday".
On November 29, 2010, Yoseob released a digital single together with Dalmatian`s Daniel titled "First Snow and First Kiss". Both were friends from their trainee years at M Boat Entertainment and had released a UCC series, "To Pick On Mr. Daniel", which became a hot topic when it was selected as no. 1 amongst the weekly TOP 5 UCCs by a sports newspaper. He also became a permanent cast member on KBS's Oh! My School (a.k.a. 100 Points out of 100), along with other idols such as MBLAQ's Lee Joon, Secret's Hyoseong, T-ara's Soyeon, Miss A's Min, and Simon D.
Yoseob was cast in his first musical as Ji Yong in Kwang Hwa Moon Love Song. The musical started its performances on March 20, 2011 and ended on April 10, 2011. He also contributed to the soundtrack of My Princess, with the song "Cherish That Person" which was released on February 7, 2011. On May 1, 2011, KBS announced plans of creating a new singing variety program featuring an all idol cast titled Immortal Songs 2 – Sing the Legends; Yang was one of the artists cast in the original line-ups. He received first place on the show’s pilot episode with his performance of “Omma (엄마, lit. Mother)“, which helped silence the critics that had dismissed his singing abilities as just a hype. However, on June 8, 2011, the show announced that Yoseob would leave the show due to his conflicting overseas promotions schedule with Beast. He expressed that although he felt extremely stressed competing against his peers, he felt regretted having to leave. Yoseob said "when we decided on the withdrawal, I did feel some relief. It was too nerve-wracking and burdensome. However, at the same time, I felt regret. I don’t think I was able to show my all. If another opportunity came by to be on the show again, I would definitely take it. I think I will. I want to show different sides of myself."
Yoseob was featured in Bang Yong Guk's first solo track, "I Remember" which was jointly composed by Bang Yong Guk and One Way’s Chance. The track has gained a lot of interest from netizens and become a hot topic. However, Yoseob was not able to sing "I Remember" with Bang Yong Gook live.
On September 27, 2011, KBS‘s ‘Poseidon‘ released part one of their original soundtrack series which featured Yoseob's vocals. His song, “No“, was a collaboration piece between Rado (of Huh Gak‘s “Hello“) and production duo Ji In and Wontag, the men behind MBLAQ’s latest releases. The song features sorrowful lyrics of a man who has no choice but to let go of his lover.
Yoseob released his solo album on November 26, 2012. All 5 songs were produced by fellow band member, Jun Hyung, including the title song, "Caffeine". A music video for "Caffeine" was released two days later, on November 28. A music video for his song "Even then, I" was released on February 14, 2013 as a valentines gift for his fans.
Yoseob has been chosen as one of the judges and coaches in Mnet The Voice Korea Kids or Voice Kids for short. The contestants will all be children between the ages of 6–14 years. He also has chosen as the most desired coach by the contestans of Voice Kids. As expected, it turns out the young contestants were eager to have someone a bit closer to their age range and more familiar to them, and thus, chose Yoseob as the coach they wanted to work with.
Yoseob is joining MBC's I Live Alone, a real-variety show that showcases the daily lives of single celebrities (men) who live alone.
Yoseob is leaving I Live Alone in which he received much love as the youngest member of the show after a short six months on broadcast due to his responsibilities and schedules as a member of BEAST. He said that due to BEAST's Japan Tour 2014, along with BEAST's upcoming comeback planned to be in April 2014, he would be unable to participate in the show.
It was announced in March 2014 that Yoseob would be participating in the musical-remake of the 2004 hit romantic comedy drama series Full House as the lead character Lee Young Jae. The musical will be on stage in April 2014.