Upon his arrival at the club in 2008, Santa Cruz made 11 league appearances for Blackburn's reserve-team until his departure in 2011.
Olimpia
2012 season
Santa Cruz debuted for Olimpia in a 0–0 draw against Tacuary on 16 June 2012. Santa Cruz was substituted onto the field for Maxi Biancucchi in the 87th minute.
Nacional Asunción
Santa Cruz made his first appearance in all competitions for Nacional during the 2014 Copa Libertadores. Santa Cruz, who had been issued the number #29 for the 2014 season, was substituted onto the field in the 89th minute for Julián Benítez in a 3–1 away group stage defeat against Colombia's Independiente Santa Fe on 11 February 2014. On 16 February 2014, Santa Cruz made his first and full league debut for Nacional in the 2014 Paraguayan Primera División season, playing a full 90 minutes of a 3–0 home victory against Sportivo Luqueño. Four days later, Santa Cruz featured as a second-half substitute in Nacional's second Copa Libertadores group stage fixture, a 1–0 home victory against Venezuela club Zamora on 20 February 2014. His first goal for Nacional came in the 71st minute of a 2–1 home victory against Sol de America on 31 March 2014. The ball had been crossed toward Santa Cruz inside the 18-yard box area who headed the ball across the face of goal into the net to win the match for Nacional. Santa Cruz scored his second league goal for Nacional in a 4–0 away victory against Club Guaraní26 April 2014. Santa Cruz had converted a penalty kick from the spot in the 70th minute. On 6 August 2014, Santa Cruz was substituted onto the field in the 70th minute for Derlis Orué during the first–leg of the 2014 Copa Libertadores Finals against Argentina's San Lorenzo and scored a last-gasp equalizer in the 93rd minute of the match to make the score line 1–1. A long ball had been played in the air from the mid-field and flicked on with the head of striker Fredy Bareiro, toward the front of the right side of the goal posts, as Santa Cruz managed to convert the goal from a tight angle with a right foot shot towards the top of the net. Santa Cruz later stated that the goal was the most important one of his career and that after the match he received a message of congratulations from older brother Roque. During the second–leg on 13 August, Santa Cruz was substituted onto the field in the 85th minute of the match for Julián Benítez as Nacional were ultimately defeated 1–0. Santa Cruz would not score again until 24 September, scoring the second goal in a 2–1 home victory against Sportivo Luqueño. He had been substituted onto the field in the 23rd minute of the first half for Armando De Giacomi, and scored in the 45th minute to give Nacional a 2–0 lead at half-time. Two weeks later, Santa Cruz scored his fourth league goal of the 2014 season against former side Deportivo Capiatá on 5 October. Santa Cruz, who was in the starting eleven of the fixture, scored in the 43rd minute to give Nacional a 1–0 lead as they went on to claim a 3–2 away victory.
Julio Santa Cruz is the younger brother of Roque Santa Cruz, Diego Santa Cruz, and the late Oscar Santa Cruz. His father, Aproniano, manages both Julio and Roque.
