Yen was born in Guangzhou, China. His mother, Bow-sim Mark, is a Fu Style Wudangquan (internal martial arts) and Tai Chi grandmaster, while his father, Klyster Yen (Zhen Yun Long ), is a newspaper editor. When he was two years old, his family moved to Hong Kong and then to Boston when he was 11. His younger sister, Chris Yen, is also a martial artist and actress, and appeared in the 2007 film Adventures of Johnny Tao: Rock Around the Dragon.

Yen describes himself as a mixed martial artist. He learned Tai Chi from a young age under his mother's tutelage. He then wanted to learn Taekwondo in his teenage years, earning a 6th Dan in the process. At the time, the Beijing Wushu Team had a scout in the United States and invited Yen over to Beijing, China, where he began training at the Beijing Sports Institute, the same facility where champion-turned-actor Jet Li trained; this is where the two of them crossed paths for the first time.  Upon his return to the United States, Yen won gold medals in various wushu competitions.  Yen later went on to discover and seek knowledge on other martial arts styles; he would later obtain black and purple belts from judo and Brazilian Jiu-Jitsu, respectively, and went on to study the art of Parkour, Wrestling, Muay Thai, Kickboxing and Boxing under various trainers. His exposure to mixed martial arts (MMA) was heightened when he went back to the United States from 2000 to 2003. While making his Hollywood debut, he also took time off to learn the various martial arts forms. Yen's progress was evident when he returned to Asia, where he implemented his newfound knowledge of MMA, showcased in films such as SPL: Sha Po Lang (2005), Flash Point (2007), and Special ID (2013).  Near the end of 2007, Yen added a new martial arts system to his arsenal. He was offered the role of Wing Chun grandmaster and mentor of film star Bruce Lee, Ip Man, in a 2008 film named after the grandmaster. He worked hard and studied Wing Chun under Ip Man's eldest son, Ip Chun, for 9 months before tackling the role. Ip Chun has since praised Yen for his effort, his skills as a martial artist, and his ability to grasp the full concept of Wing Chun much faster than anyone else he has taught.  Yen believes that combining many martial arts together will produce the most effective and harmonious style. Yen has said, "When you watch my films, you're feeling my heart." He believes in practical combat, and in his opinion, MMA is the most authentic type of practical combat. He has mentioned that he would have competed in the Ultimate Fighting Championship if he did not have a recurring shoulder injury.

how long did he train there?