On 18 December 2011, in only his second appearance, he scored his professional goal by netting a last-minute equalizer in a 2–2 home draw against Cerro Porteño.[3] He then became a regular starter from the 2012 season onwards.
On 1 July 2014, Domínguez was loaned to Nacional for the remainder of the 2014 Copa Libertadores.[4] On 15 August, after the club was knocked out, he returned to his parent club, having only made two appearances.[5]
Cerro Porteño
On 20 December 2014, Domínguez moved to Cerro Porteño for a US$ 750,000 fee for 50% of his federative rights.[6] Regularly used, he scored a career-best 19 goals during the 2016 campaign; highlights included braces against Deportivo Capiatá (3–2 and 2–1 home wins), River Plate (3–2 away win) and former side Nacional (6–1 away win).
He also had a great Copa Sudamericana campaign, where he scored six goals in seven matches. His tally began with a hat trick against Independiente Santa Fe in the round of 16, two goals in the quarter finals first leg against Independiente Medellín, and a goal in the semi-finals against eventual winners Atlético Nacional, finishing tied for the golden boot with Miguel Borja.[7]
América
On 14 January 2017, Mexican side Club América signed Domínguez on a four-year contract.[8] He made his debut abroad fourteen days later, starting and scoring the only goal of the match in a Liga MX home win against Veracruz.[9]
On 29 July 2017, Domínguez scored a brace in a 2–0 away win against Pachuca.[10]
Independiente
On 24 January 2019, Domínguez joined Argentine club Independiente on a deal worth US$6 million, becoming the club's all-time record signing.[11]
Austin FC
On 24 August 2020, Domínguez was announced as the first Designated Player of the newly formed MLS franchise Austin FC, set to make its competitive debut in 2021.[12] On 31 August 2020, it was announced that Domínguez would spend the remainder of the season on loan with Guaraní, returning to Paraguay after three years.[13] He left the club in December 2020 after his loan concluded and joined Austin FC for their inaugural season.
On 24 April 2021, Domínguez scored two goals for Austin against the Colorado Rapids in the club's first ever victory.[14]
Domínguez started the 2022 season off strong with two goals in his first four games, but was sidelined when the MLS suspended him on April, starting an investigation into an off-field incident regarding domestic violence.[15] On May 4, he was reinstated into the Austin FC squad and began training with the rest of the team.[16][17] However, on 23 July 2022, the club announced that they had reached an agreement with Domínguez to terminate his contract.[18]
^"Cecilio retornó a Sol" [Cecilio returned to Sol] (in Spanish). Hoy. 15 August 2014. Retrieved 13 January 2019.
^"Mendieta y Cecilio ya son del Ciclón" [Mendieta and Cecilio are already from Ciclón] (in Spanish). ABC Color. 20 December 2014. Retrieved 13 January 2019.