2019–2020: Major debut and first win in doubles Guinard made his Grand Slam tournament main draw debut at the
2019 French Open after receiving a wildcard for the doubles main draw, partnering
Arthur Rinderknech. At the
2020 French Open he reached the second round for his first Grand Slam tournament win in doubles also as a wildcard partnering Rinderknech.
2021: First Challenger final, Top 250 Guinard made his first Challenger final at the
2021 Open du Pays d'Aix where he lost to
Carlos Taberner. He reached the top 250 on 8 November 2021 at world No. 247.
2022: French Open singles debut, Top 150 in singles & doubles Guinard reached a career-high doubles ranking of world No. 155 on 17 January 2022, after winning the
2022 Traralgon International with
Zdeněk Kolář. In March, he won his maiden singles
2022 Challenger di Roseto degli Abruzzi II title as an alternate. In April, Guinard made his ATP debut as a lucky loser at the
2022 Barcelona Open Banc Sabadell, where he lost to
Hugo Dellien. He reached a career-high singles ranking of No. 151 on 25 April 2022. In May, Guinard was awarded wildcards into the main draw of the
2022 French Open in singles and doubles partnering
Enzo Couacaud. Guinard qualified for the
2022 ATP Lyon Open main draw and defeated compatriot world No. 68 and wildcard
Hugo Gaston in the first round for his first tour-level win. He went on to defeat
Michael Mmoh in the next round to reach the quarterfinals for the first time in his career. As a result, he reached the top 150 in the singles rankings.
2023–2024: Two ATP finals in doubles, Challenger titles In July 2023, Guinard won the
2023 Internationaux de Tennis de Troyes as a qualifier, defeating fellow countryman
Calvin Hemery in the final. This was Guinard's first final on the
ATP Challenger Tour in more than a year, allowing him to return into the Top 300 in the singles rankings. He also won the doubles title at the same tournament. In six months starting in June 2023, Guinard won four doubles
Challenger titles, and then another two in January 2024 (five of the titles won were with
Grégoire Jacq). In March 2024, he won one more Challenger in
Zadar also with Jacq. The French pair Guinard/Jacq entered their home Slam, the
2024 French Open as alternates, and on their Major debut as a team, defeated 14th seeded American pair of
Nathaniel Lammons and
Jackson Withrow in the first round. They reached the third round with a win over
Guido Andreozzi and
Rinky Hijikata. They lost to
the Tsitsipas brothers. As a result, Guinard reached the top 100 at world No. 92 in doubles on 10 June 2024. Guinard reached his first ATP final with Jacq at the
2024 Swedish Open defeating defending champions and top seeded pair of
Aleksandr Nedovyesov and
Gonzalo Escobar. They lost to Brazilian duo
Rafael Matos and
Orlando Luz. The following week the pair reached their second ATP final at the
2024 Croatia Open Umag. Following one more Challenger final in
Cassis, France, Guinard reached the top 70 in the doubles rankings on 9 September 2024. In November 2024, Guinard played his first
ATP Tour singles tournament in more than two years by entering the main draw of the
2024 Moselle Open as a lucky loser, losing in the first round to
Zizou Bergs.In doubles at the same tournament, he lost with Gregoire Jacq to French duo, compatriots Herbert/Olivetti in the quarterfinals.
2025–2026: Major mixed final, two Masters doubles titles Ranked No. 261, Guinard also entered as a lucky loser the main draw of the
2025 Adelaide International and defeated
Roman Safiullin, having entered the tournament as alternate in the qualifying stage. He lost to top seed
Tommy Paul in three sets. In April 2025, Guinard won his maiden
ATP Tour title at the
2025 Monte-Carlo Masters partnering
Romain Arneodo, as a wildcard pair. They defeated
Rohan Bopanna and
Ben Shelton in the quarterfinal, and second seeds
Harri Heliovaara and
Henry Patten in the semifinal. They then defeated seventh seeds
Julian Cash and
Lloyd Glasspool for the title. It was only the pair's second tournament playing together. As a result, Guinard entered the top 40 on 14 April 2025. In July, Guinard won his second
ATP Tour title at the
Croatia Open Umag partnering Romain Arneodo. The pair defeated
Patrik Trhac and
Marcus Willis in the final. Guinard reached his second Masters 1000 semifinal at the
2025 Rolex Shanghai Masters with new partner
Guido Andreozzi as an alternate pair, upsetting second seeds
Harri Heliövaara/
Henry Patten, but lost to
Kevin Krawietz/
Tim Puetz. Guinard finished the 2025 season ranked No. 24 on 17 November 2025. At the
2026 BNP Paribas Open, Guinard won his second Masters title, and biggest of his career, with partner Andreozzi, over top seeds
Horacio Zeballos and
Marcel Granollers in the semifinals, and
Arthur Rinderknech and
Valentin Vacherot in the final. It was also Guinard's third ATP Tour title. As a result, he reached the top 15 at world No. 14 in the doubles rankings on 16 March 2026. ==Performance timelines==