He became the first Portuguese player to maintain top-100 status by playing exclusively on the ATP World Tour in a single season.
At the 2015 Australian Open, he started his campaign with wins over wild card Jordan Thompson and Martin Kližan.
He won his first singles match over Maxim Dubarenco and the doubles match with Gastão Elias.
Sousa beat Frenchman Julien Benneteau in three sets in the final after saving one match point, becoming the first Portuguese player to win an ATP World Tour singles tournament. The previous record holder was Rui Machado, who was world No. Later in January, Sousa joined the Portugal Davis Cup team to face Slovenia for the Europe/Africa Group I 1st Round.
During the North American hard court Masters swing in March, Sousa started the Indian Wells Masters with a win over Aleksandr Nedovyesov, followed with a second-round loss to 20th seed Ernests Gulbis.