In November, Sugita won back-to-back Futures titles in Thailand, and reached final in the Toyota Challenger, but lost to fellow Japanese Tatsuma Ito in straight sets.

Sugita started the season by playing the Chennai Open as qualifier, and recorded his first ATP main draw win against Dustin Brown in three sets.

Yūichi started his 2012 campaign by making it to the quarterfinals of the Chennai Open before falling to Nicolás Almagro in three close sets, knocking out eighth seed Oliver Rochus and Lu Yen-hsun on the way.

Sugita won through the opening round in the Hall of Fame Tennis Championships, against Canadian Jesse Levine in straight sets.

In later season, Sugita earned men's singles bronze medal in the 2014 Asian Games at Incheon, where he beat Temur Ismailov of Uzbekistan in the quarterfinal.

Sugita won through the qualifying at the 2015 Wimbledon Championships for the second consecutive year in this tournament, losing to Blaž Kavčič in the first round.

Sugita qualified for the 2016 Australian Open main draw for the first time,[8] but lost to 23rd seed Gaël Monfils in the first round.

In April he made it into the main draw of the Barcelona Masters as a "Lucky Loser", and went on to defeat Tommy Robredo, Richard Gasquet and Pablo Carreño Busta before losing to Dominic Thiem in the quarter-finals.

In the final Sugita defeated Adrian Mannarino 6–1, 7–6, becoming the third Japanese man to win an ATP title, preceded by Shuzo Matsuoka and Kei Nishikori.

He beat Brydan Klein in Wimbledon, marking the first time he'd reached the second round of a Grand Slam tournament, losing next up to Mannarino.

In August, Sugita won two rounds in the Masters 1000 tournament at Cincinnati before losing to eventual champion Grigor Dimitrov.

He lost his singles match to Roger Federer 6–4, 6–3, but his leaping overhead smash delighted the fans and was included in most compilation clips of early 2018 season highlights.

At the 2018 Australian Open Sugita earned his first win over a Top 10 player by defeating world number 9 Jack Sock in four sets.

In April he lost in the first round to Jan-Lennard Struff at Monte-Carlo, Guillermo García López at Barcelona, and Yannick Maden in Munich.

Later in the month he lost in the second round in s-Hertogenbosch to Marius Copil; and the following week at Halle beat world #7 Dominic Thiem in straight sets, in what he said was "my best match in my career", before losing in the quarterfinal to Denis Kudla.

In October he received a wild card entry into the Tokyo Open, and lost in the first round to countryman Kei Nishikori.

[10] In October, Sugita lost in the qualifying rounds for the Stockholm Open, but made it into the main draw as a lucky loser and then won three matches before losing in the semifinals.

In January he started the year by reaching the final of the ATP Challenger Tour event in Nouméa, where he lost to J. J. Wolf.

In March, in a Challenger Tour event in Lugano, Switzerland, he won three rounds and then lost in the semi-final to eventual champion Dominic Stephan Stricker.

He received an entry into the main draw as a lucky loser, where he lost in the first round to number eight seed Casper Ruud.