He won the 2015 Open d'Italia on the European Tour after winning a play-off against Martin Kaymer.

[2][3] Later in the year, he won his second Asian Tour title at the Hero Honda Indian Open.

Karlberg earned a 2015 European Tour card through qualifying school, and won the Open d'Italia during his rookie season, after holing a birdie putt on the second extra hole in a play-off against Martin Kaymer.

After battling illness which forced him to step away from competitive golf, he holed a 50-foot birdie putt on the final hole of 2019 Qualifying School to earn the final European Tour card for 2020.

The achievement earned him €314,170 in prize money and a late spot at The 149th Open Championship two weeks later.