As a teenager, he won the US Junior National Championship and enjoyed success on the ATP Challenger Tour, reaching nine finals and winning four titles.

In 1999, his father began working as a day laborer on a construction crew that built the Junior Tennis Champions Center (JTCC) in College Park, Maryland.

[15] The following year, in December 2013, Tiafoe became the youngest player to win the Orange Bowl, one of the highest-tier Grade A events on the ITF Junior Circuit.

[19] Tiafoe produced his best result at a junior Grand Slam tournament at the US Open, where he reached the semifinals before losing a tight match to Quentin Halys.

Tiafoe's performance at these events was good enough to win the 2015 Har-Tru Challenge and earn the only American wildcard spot into the main draw of the 2015 French Open.

[30] At the Winston-Salem Open in August, Tiafoe entered the main draw as a qualifier and won his first ATP Tour-level match, after defeating James Duckworth in a third-set tiebreaker.

At the Indian Wells Masters, Tiafoe was awarded a wild card into the main draw and won his first-round match against his compatriot rival, No.

[34] Tiafoe's best performance in the clay-court season came at Tallahassee where he avenged his loss to Facundo Arguello in the final the previous year by knocking him out in the first round.

[35] Tiafoe began his return to the North American hardcourts by reaching his second Challenger final of the year at Winnetka before losing to top-seeded Yoshihito Nishioka.

[37] In October, Tiafoe cracked the top 100 for the first time by winning the maiden event at Stockton, defeating fellow American Noah Rubin in the final.

[39] At the Australian Open, Tiafoe began the year by reaching the main draw of a Grand Slam through qualifying for the first time and then recording his first career major match win over Mikhail Kukushkin.

[40] To close out the winter hard court season, he also qualified for the Miami Masters and won his first round match before falling to Roger Federer.

[42] He began with the US Men's Clay Court Championships in Houston, where he reached his first career ATP final in the doubles event, after partnering with veteran Dustin Brown as a wildcard entry.

[45] In September, captain John McEnroe chose Tiafoe to replace Juan Martín del Potro for Team World in the inaugural Laver Cup, which mostly featured players in the top-25 of the ATP rankings.

[47] Tiafoe achieved a year-end ranking inside the top 100 for the first time, but only managed to be named the first alternate for the inaugural Next Generation ATP Finals.

[49] At the inaugural New York Open, Tiafoe reached his first career quarterfinal at an ATP Tour-level event before losing to top seed Kevin Anderson.

The following week, Tiafoe entered the Delray Beach Open as a wildcard and won his first ATP title after beating Peter Gojowczyk in the final.

[85] At the Canadian Open, Tiafoe lost in the second round of qualifying to Emil Ruusuvuori, but was awarded a lucky-loser spot in the main draw after fellow American Sebastian Korda withdrew.

In the main draw, Tiafoe beat Dušan Lajović in the first round before winning his second match of the year against Tsitsipas, after recovering from a break down in the third set.

Tiafoe, who had played in the French Open six times previously, recorded his first victory at Roland Garros in 2022 with a first-round win over Benjamin Bonzi.

[99] In his next event, at his home tournament of Washington, Tiafoe reached the quarterfinals, but let five match points slip away and lost to Nick Kyrgios in three sets.

Due to multiple rain delays, he played and won four matches all in straight sets over the course of two days, defeating Gijs Brouwer in less than an hour in the semifinal[117] and Tomás Martín Etcheverry in the final.

Tiafoe reached the semifinals at his home tournament, the Delray Beach Open, losing to third seed and compatriot Tommy Paul, the eventual runner-up.

He reached his first Masters and biggest final of his career with a three-set stunning defeat of 15th seed Holger Rune, coming from behind in the third set and saving two match points.

Following his second round loss to Roman Safiullin, Tiafoe abused the umpire verbally after receiving several warnings during the match for exceeding the time allowed to serve.

[146][147] Like many of his top-ranked American contemporaries such as Jack Sock and Sam Querrey,[148][149] Tiafoe plays an aggressive offensive game that relies on a big serve and powerful forehand.

[152] After facing him at the 2016 US Open, John Isner said that Tiafoe could return his serve — widely regarded as one of the best in the game — as well as any player on tour outside of Novak Djokovic.

[154] After Tiafoe moved to Florida to train with the USTA, he was coached by José Higueras from Spain, who had led fellow Americans Michael Chang and Jim Courier to Grand Slam titles.

[171][172] After Tiafoe defeated Rafael Nadal and reached the semifinals of the US Open in 2022, he attended a Maryland Terrapins Football game where he was honored for his accomplishments.

[176][177][178] Tiafoe has embraced his position both as one of the few players of color on the ATP Tour and as a potential role model to youngsters in general, saying, "That's one of my biggest motivations – to get more black people playing tennis...