[2] Representing Italy, he was part of the Italian squad winning the 2023 Davis Cup and won the Gold Medal at the 2022 Mediterranean Games in men singles.

[4] He won his maiden Challenger title at the 2022 Internazionali di Tennis d'Abruzzo as a wildcard defeating Francesco Maestrelli.

4 and third seed Casper Ruud in straight sets for his first career top-10 win, to reach the third round of a Masters for the first time.

[10] On his Grand Slam debut he qualified for the 2023 French Open and recorded his first win against Daniel Elahi Galán.

[12] In Toronto, Arnaldi qualified and recorded his first ever Masters 1000 win on hard courts beating local wildcard Vasek Pospisil in the first round, then fell to World No.

At the 2023 Rolex Shanghai Masters he defeated Alexei Popyrin and upset 21st seed Jan-Lennard Struff to reach the third round.

43 at the 2024 Delray Beach Open he defeated Yoshihito Nishioka firing 21 aces and recording 50 winners.

At the beginning of the clay season, at the 2024 Barcelona Open Banc Sabadell, he reached the quarterfinals with a defeat of Arthur Cazaux by retirement, and of two Argentines, eight seed Sebastian Baez and qualifier Marco Trungelliti.

In May, at the 2024 French Open he upset sixth seed Andrey Rublev to reach the fourth round for the first time at this Major.

[19] At the 2024 National Bank Open he reached the semifinals for the first time at a Masters level, having never get past the fourth round, defeating qualifier Mackenzie McDonald and upsetting 16th seed Karen Khachanov, previous year semifinalist Alejandro Davidovich Fokina by retirement and Kei Nishikori.