In June 2016, Blackstenius was named in the Sweden squad for the 2016 Summer Olympics. Having appeared as a substitute against South Africa in the opening group match, Blackstenius was an unused substitute for the next two as Sweden progressed as one of the two best-ranked third place teams. In the quarter-final against the reigning World Cup and Olympic champions United States, she came of the bench to replace the injured Fridolina Rolfö in the 18th minute and scored in the second half to give Sweden a lead. With the game tied at 1–1, Sweden progressed following a penalty shoot-out. Coming on again as a substitute in the Gold Medal match, Blackstenius scored in the 67th minute to pull Sweden within one score of Germany. The game finished 2–1 with Sweden winning the silver medal.