Dellacqua commenced the season at the Hopman Cup, losing all three rubbers to Agnieszka Radwańska, Alizé Cornet and Heather Watson. She then played the Hobart International where she was the top seed for the first time at a WTA Tour event. She lost in the second round. Dellacqua then played at the Australian Open as the 29th seed. She defeated Yvonne Meusburger in straight sets before losing to eventual semifinalist Madison Keys. She also played in the women's doubles as the 15th seed with Kimiko Date-Krumm. They lost in the second round. She then traveled to Stuttgart for the 2015 Fed Cup World Group where she played in the doubles, losing to the partnership of Görges/Lisicki. Dellacqua next played the Dubai Tennis Championships losing in the second round to Lucie Šafářová despite winning the first set. She then traveled to the Qatar Total Open where she lost in the first round to Venus Williams again after taking the first set. She next played at the Malaysian Open as the 3rd seed but lost in the first round to eventual semifinalist Hsieh Su-wei. Dellacqua then withdrew from the BNP Paribas Open where she was defending quarterfinalist points. This saw her fall down to 42nd in the WTA rankings. Despite this she was the 32nd seed at the Miami Open where she lost in the second round (after having a first round bye) to Belinda Bencic in three sets.