Who is Learner Tien? All about the teenager who played in community courts in California before pulling off the biggest upset of Australian Open 2025

Learner Tien pulled off the biggest upset of the 2025 Australian Open yet on Thursday, beating former World No. 1 Daniil Medvedev in the second round in a five-set thriller.

Tien, currently ranked World No. 121, was born in December 2005 in California. The American's parents are originally from Vietnam, and have since immigrated to the USA. His mother Huyen, a math school teacher, named him Learner as a tribute to her profession. Interestingly, his sister is named Justice, a tribute to their father Khuong's job as an attorney.

Having started playing tennis at the very young age of five in the community courts of California, Tien enjoyed a successful career in junior tennis. He reached the final of the Australian Open and US Open boy's singles in 2023, and also reached a career-high of No. 4 in both singles and doubles on the junior level.

He enjoyed major success in 2024, winning three ATP Challenger titles and qualifying for the ATP Next Gen Finals in Jeddah. However, he lost to Joao Fonseca in the final. As a result of his breakthrough year, he reached a career-high ranking of World No. 114 that year.

In 2025, he made his Australian Open debut, two years after his US Open debut. Tien, in an interview with the ATP, spoke about all the lessons he has learnt in 2024, commenting on how he has started to believe in himself after seeing his hard work on the sidelines finally pay off.

"I think just trusting what I'm doing. Just really believing in what I am putting in and eventually, whether it's now or down the road, that it will pay off. I had an injury earlier this year and I was out for a few months. So I'm kind of behind, but I know that if I just keep working to get back I'll inevitably achieve," Learner Tien said.

"I think that it's been huge for me just to have decent bit of success the past few months and see my work pay off. I think it's been very motivating and it's been a good lesson for me to just plug away and trust that what I'm doing is going to pay off," he added.

Quite surprisingly, the 19-year-old has credited Carlos Alcaraz for drawing him into watching more tennis, hailing the Spaniard for his entertaining style.

"When I first started getting into tennis, watching tennis — and I didn't for a while, until I was probably 15, 16 — it was probably [Carlos] Alcaraz. He really drew me into watching tennis at first. I guess the entertainment factor drew me in and I obviously started understanding tennis better watching all these guys. I really appreciated watching these matches a lot more," Learner Tien said.

Learner Tien credits his parents for introducing him to tennis

2025 Australian Open - Day 5 - Source: Getty

Learner Tien has credited his parents for his tennis career, thanking them for introducing him to the sport very early on. His father Khuong, in fact, coached him until he was 12 years of age before he got into the USTA program to hone his skills better.

"My parents have been key. They introduced me to the sport, integrated me in. I am the youngest in my family and everyone played tennis before I did, so I was just following them. My dad was my coach until I was probably 11 or 12 and still had a big say in my tennis for a while after that. I definitely give a lot of credit to my dad for that," Learner Tien said to the ATP.

On Thursday, Tien won 6-3, 7-6(4), 6-7(8), 1-6, 7-6(10-7) against Daniil Medvedev, making it the biggest win of his young career yet.