Wallin had a successful amateur career and was runner-up at the 2018 Fairhaven Trophy and the 2019 Grand Prix de PACA.

He defeated top-ranked Gordon Sargent in extra hole in the team's quarterfinal match to send the Buckeyes to the semifinals.

[4] Wallin won silver at the 2022 European Amateur Team Championship in England, after Sweden lost the final to Spain 41⁄2 to 21⁄2.

[5] He finished in second place behind Italy and ahead of the United States in third at the 2022 Eisenhower Trophy, in a team together with Ludvig Åberg and Tobias Jonsson.

[7] Wallin turned professional after graduating in 2024 and joined the Nordic Golf League, where he was runner-up at Holtsmark Open in Norway.