Stefan Kozlov Bio
Stefan Kozlov is an American professional tennis player of Russian descent who has competed on the ATP Tour and at the Challenger level since 2013. Born on 1 February 1998 in Skopje, Republic of Macedonia, he relocated to the United States as a child and currently resides in Pembroke Pines, Florida. Right-handed with a two-handed backhand, Kozlov reached a career-high ATP singles ranking of world No. 103 in July 2022 and has built his career on a foundation of strong junior results and consistent Challenger-level success.
Across junior and professional tennis, Kozlov has recorded wins over top-tier opponents, captured multiple Challenger titles, and become a steady presence in American tennis. He is recognized for his competitive baseline game and his longevity on tour despite the challenges of a demanding professional schedule.
Early Life and Background
Stefan Kozlov was born on 1 February 1998 in Skopje, the capital of the Republic of Macedonia, to a family of Russian heritage. His father, Andrei Kozlov, is a tennis coach who introduced Stefan to the sport at a young age and has played a central role in his development. Kozlov also has a brother, Boris, who has also pursued tennis at a competitive level, making the household a deeply tennis-oriented one.
Relocating from Skopje to the United States during his childhood, Kozlov grew up and settled in Pembroke Pines, Florida, where he continues to base his training. The Florida tennis environment, combined with his father’s coaching, provided the structure and competition he needed to sharpen his game from an early age. Standing 1.83 m (6 ft 0 in) tall, Kozlov developed a physical presence that complemented his technical foundation.
His early exposure to high-level training and the guidance of his father set the stage for a rapid rise through the junior ranks, where his talent became evident in national and international competition.
Path to Tennis
Kozlov’s competitive path accelerated quickly as a junior. In 2014, he reached two junior Grand Slam finals, finishing as runner-up to Alexander Zverev at the Australian Open and to Noah Rubin at Wimbledon. These results propelled him to a year-end junior ITF Combined ranking of No. 3, signaling his arrival as one of the top young players in the world.
That same year, Kozlov reached his first ATP Challenger final in Sacramento, where he fell to Sam Querrey, and won seven ITF Futures finals across his development years. He also partnered with Noah Rubin to win the U18 National Championships doubles title, earning a wildcard into the 2014 US Open main draw. In 2015, he reached the final of the U18 National Championships, losing to Frances Tiafoe in five sets, a result that underlined his competitive toughness against future tour regulars.
By the time he turned professional in 2013, Kozlov had already accumulated a reputation as a poised, technically sound prospect with the game to compete at higher levels.
Stefan Kozlov Career
Early Career (2013–2015)
Kozlov made his ATP World Tour debut as a wildcard at the 2013 Hall of Fame Tennis Championships in Newport at just 15 years old, losing in the first round. The experience marked the beginning of his transition from junior standout to professional competitor, and he continued to test himself against higher-ranked opposition whenever wildcards and qualifying opportunities arose.
During this period, he defeated his first top-100 player, Tim Smyczek, in 2014, a milestone that demonstrated his readiness for the next level. He balanced ATP main-draw appearances with a busy Challenger and Futures schedule, collecting four ITF Futures titles and using the circuit to build match experience and ranking points.
ATP Breakthrough (2016–2017)
In 2016, Kozlov secured his first career ATP-level match win as a wildcard at the Ricoh Open in Den Bosch, defeating Steve Johnson along the way to his first career ATP quarterfinal. Later in the season, he reached a Challenger final in Suzhou and won his first Challenger title in Columbus, announcing his arrival on the Challenger circuit.
He followed this with a second Challenger title at the 2017 Las Vegas Challenger, reinforcing his consistency at that level. The same year, he reached a career-high doubles ranking of No. 180 on 19 June 2017, showing that his game translated effectively to both disciplines.
Return to Form (2021)
Kozlov’s 2021 season marked a strong resurgence. He won the Columbus Challenger in September, defeating Max Purcell in the final in three sets, and also won the doubles title at the same event partnering with Peter Polansky. He added a second Challenger title at the Charlottesville Men’s Pro Challenger, beating Aleksandar Vukic, and closed the year with a third Challenger crown in Champaign.
These results returned him to the top 200 in the ATP rankings for the first time in more than three years, finishing 2021 at No. 159 and earning a main-draw wildcard into the 2022 Australian Open.
Career-High Year (2022)
At the 2022 Australian Open, Kozlov made his Grand Slam singles debut as a wildcard and recorded his first major win against Jiří Veselý before falling to seventh seed Matteo Berrettini in the second round. As a qualifier at the Delray Beach Open, he reached his second career ATP quarterfinal after defeating Emilio Gómez and Steve Johnson.
His biggest career win came at the 2022 Abierto Mexicano Telcel in Acapulco, where, ranked No. 130, he upset Grigor Dimitrov in three sets in the longest match in tournament history. He also made his Wimbledon debut as a lucky loser, losing to twelfth seed Diego Schwartzman, and reached a new career-high singles ranking of No. 103 on 18 July 2022.
Champaign Era (2025)
Kozlov continued to compete on the Challenger circuit in 2025, winning his sixth career Challenger title at the Champaign Challenger. The victory marked his first Challenger crown since 2021, when he also won the same event, demonstrating his enduring comfort and success at that tournament.
Driving Style and Strengths
Kozlov plays a right-handed game built around a two-handed backhand, with a baseline style that rewards patience and consistency. His competitive doubles results, including a career-high No. 180 ranking, reflect strong net instincts and tactical flexibility, and his upset wins over top opposition such as Grigor Dimitrov and Steve Johnson show a comfort level against big-game opponents.
Notable Events and Milestones
Signature moments include his 2014 junior Grand Slam finals appearances, his first ATP match win in 2016 in Den Bosch, his marathon upset of Grigor Dimitrov in Acapulco in 2022, and his sixth career Challenger title at the 2025 Champaign Challenger. His career-high ranking of No. 103 in July 2022 remains the benchmark of his singles career.
Stefan Kozlov Career Wins
Stefan Kozlov has built a steady resume of titles and deep runs at the Challenger and ITF level, complemented by a small number of notable ATP-level wins. His career prize money totals $1,058,176, reflecting sustained presence on professional circuits since 2013.
ATP Challenger and ITF Highlights
Kozlov has captured six ATP Challenger titles, including his first in Columbus in 2016, followed by wins in Las Vegas (2017), Columbus (2021), Charlottesville (2021), and Champaign (2021 and 2025). He has also won four ITF Futures titles during his developmental years, giving him a foundation of success across multiple tiers of the professional game.
His most recent Challenger title came at the 2025 Champaign Challenger, where he won the event for the second time in his career. These Challenger results have been central to his ranking progression and to his ability to qualify for ATP main draws.
Other Wins and Performances
Beyond Challenger titles, Kozlov has reached additional Challenger finals and recorded qualifying wins at Grand Slams, including reaching the second round of qualifying at the 2017 French Open. He has also reached ATP quarterfinals at Delray Beach and ‘s-Hertogenbosch, and recorded a first-round doubles appearance at the 2014 US Open.
Stefan Kozlov Family
Family Background and Racing Lineage
Kozlov comes from a family of Russian heritage with deep ties to tennis. His father, Andrei Kozlov, is a tennis coach who has been a central figure in Stefan’s development, and his brother, Boris, is also a tennis player, making the family a competitive tennis household.
Personal Life
Stefan Kozlov resides in Pembroke Pines, Florida, where he continues to train and compete on the professional circuit. He was born in Skopje, Republic of Macedonia, and moved to the United States as a child, building his career from a Florida base alongside his family.
2025 Season Performance
Kozlov’s 2025 season has been anchored by consistent Challenger-level competition, with a return to form highlighted by his sixth career Challenger title at the Champaign Challenger. The title, his first Challenger crown since 2021, demonstrated that he remains a competitive force on the circuit and capable of winning titles against a deep Challenger field.
His current ATP singles ranking stood at No. 306 as of 17 November 2025, reflecting a year in which he has continued to accumulate match wins and ranking points through Challenger events. The Champaign title offered momentum heading into the close of the season and reinforced his standing as a familiar name in American tennis.
Looking ahead, Kozlov’s pathway back toward the top 200 and beyond will continue to run through Challenger results, with the goal of securing direct entry into ATP main draws and Grand Slam qualifying draws. His experience, baseline consistency, and proven record of winning Challenger titles position him to remain a steady competitor on the circuit in the seasons to come.