During his time with the band, he also featured in other singers' works; the rap for Brave Brothers' "Finally" and Hye Ji's "Your Love".
On February 23, 2011, NH Media confirmed and released a statement that Alexander and his bandmate Ki Bum had left the group.
He then released his first single "I Just" in December, and made his solo debut through a showcase held at the Akasaka Blitz in Tokyo, Japan.
[citation needed] In 2013, Alexander and Calvin Chen both sang the OST of Singaporean film "3 Peas in a Pod", "You and I" and" 我与你" in Korean and Mandarin respectively.
In 2012, he ventured into acting through a Korean drama on Channel A, "Immortal Classic", playing the role of a foreigner who wants to learn about Kimchi, and in the following year, he made a guest appearance in OCN's "God's Quiz Season 3" Episode 6.
In 2017, he became the leading man in a Philippine TV series of GMA Network entitled My Korean Jagiya, alongside Filipina actress Heart Evangelista.
Alexander hosted Arirang TV's radio show Pops in Seoul segment 'All About You' and 'Radio School' with bandmates Kevin and Eli during his time with U-Kiss.
Currently, he is hosting a k-beauty show "Stylecast" on Arirang TV, alongside Ashley Choi from Ladies' Code, and also a daily radio programme on tbs eFM, "Double Date", with Superstar K7 winner Kevin Oh.
In 2015, he was a regular guest for Guizhou TV's "Perfect Dating" (贵州卫视 “非常完美”) In 2009, Alexander walked the runway for the FEEL KOREA, K-POP Night & K-Fashion show in Shanghai, as well as at the Seoul Fashion Week 2011 S/S.