In the 2015 Wimbledon Boys' Doubles, Ruud made it to the semifinals together with partner Miomir Kecmanović, before losing to eventual champions Lý Hoàng Nam and Sumit Nagal.

In 2016, Ruud and Kecmanović reached the semifinals of the 2016 French Open Boys' Doubles before losing to Chung Yun-seong and Orlando Luz.

[6] In September, in his first ever ATP Challenger tournament, Ruud managed to win the Copa Sevilla after beating Taro Daniel in the final.

Due to his win in his Challenger debut, Ruud received a wildcard to the 2016 Chengdu Open, his first ATP World Tour 250 series tournament.

[9] After impressing in 2016 and climbing the ATP ranking, Ruud lost in the third and final qualifying round of the 2017 Australian Open to Reilly Opelka.

The following week he reached the semifinal of the Brasil Open, beating Thiago Monteiro, top seed João Sousa and Hugo Dellien before losing to Christian Garín in two sets.

After coming through the qualifiers he went on to beat Dan Evans[12] and Nick Kyrgios before losing in the third round to Juan Martín del Potro in straight sets.

At the French Open, Ruud beat Ernests Gulbis and 29th seed Matteo Berrettini before losing in straight sets against Roger Federer in the third round.

Ruud also reached the second round at the doubles event alongside Miomir Kecmanović after knocking out former winners and 12th seed Ivan Dodig and Édouard Roger-Vasselin before losing in three sets to Federico Delbonis and Guillermo Durán.

[15][16] Two weeks after his first title, Ruud reached his second final in a month at the Chile Open but lost in three sets against Thiago Seyboth Wild.

He then defeated Pablo Carreño Busta and defending champion Fabio Fognini[20] to reach his second Masters 1000 semifinal, where he lost to Andrey Rublev.

Ruud would then claim victory a week later in Kitzbühel, defeating Pedro Martínez in the final, to win his fourth title of the season and fifth of his career.

His third round victory over Marcos Giron confirmed Ruud's spot at the ATP Finals, where he made his debut at the year-end championships.

At the ATP Finals, Ruud reached the semifinals after losing to Novak Djokovic before beating Cameron Norrie and Andrey Rublev in the round robin.

Ruud was drawn to play Alex Molčan on the first round in Australian Open, however, he withdrew due to an ankle injury sustained during the practice.

Shortly after his recovery, he entered the Argentina Open at which he defeated Diego Schwartzman in the final and clinched his seventh career ATP singles title.

He reached his fourth Masters 1000 semifinal at the Miami Open by defeating Henri Laaksonen, Alexander Bublik, and Cameron Norrie, and later earning his first win against world No.

[32] He next defended his title at the Geneva Open, defeating João Sousa in the longest championship match of the season in both time (3 hours 4 minutes) and games (36).

[36] In the first all-Scandinavian French Open quarterfinal, he defeated Holger Rune to set up a match with also first-time Roland Garros semifinalist Marin Čilić.

[40] In July, Ruud won the Swiss Open Gstaad for the second year in a row and his ninth ATP title overall, after defeating Matteo Berrettini in the final, improving his tour-level record in Switzerland to 16–0.

[44] He then defeated lucky loser Corentin Moutet, 13th seed Matteo Berrettini, the latter in straight sets, to make his second major semifinal appearance.

In January 2023, Ruud criticized the length of the ATP Tour calendar and said he would take around a month's break from competition after the 2023 Australian Open, with February effectively his pre-season.

[51] During the early North American swing, he struggled to find form after losing in the second round of the Mexican Open to Taro Daniel in straight sets.

Ruud won his tenth ATP title at the clay court 2023 Estoril Open defeating home favorite and wildcard Joao Sousa, defending champion and fifth seed Sebastian Baez, Quentin Halys in the semifinal in a tough three set match, eventually emerging victorious in the third set tiebreaker and Miomir Kecmanović in the final.

[52] En route he recorded his 100th clay court win in the first round, becoming just the second man born in 1995 or later to hit that number, after Alexander Zverev.

At the 2023 French Open, Ruud defeated Elias Ymer, qualifier Giulio Zeppieri, Zhang Zhizhen, and Nicolás Jarry to advance to the quarterfinals for a second year in a row at this Major.

[59] After defeating qualifier Laurent Lokoli in the first round, he again experienced a disappointing early exit from the event in the second, falling to the 142nd-ranked player in the world, Liam Broady, in five sets.

At the United Cup, Ruud defeated Tallon Griekspoor and Borna Ćorić in straight sets to lead Team Norway to the quarterfinals.

[64] At the next tournament the 2024 Abierto Mexicano Telcel in Acapulco he reached back-to-back finals and his 20th career one overall with a win over second seed Holger Rune.

[68] At the Paris Olympics he became the first Norwegian player to reach the quarterfinals stage at the Games, recording his 250th career win over Francisco Cerúndolo.