Mallo started his career in 2014 with Liverpool, making his debut in a Uruguayan Segunda División match against Progreso, in a 6–0 win.[2] That same season, his team secure promotion to the Uruguayan Primera División by winning 2014-15 second division.[3]
On 30 October 2020, Mallo returned to Uruguay, joining Defensor Sporting on a free transfer and signing a contract until December 2021.[7] On 29 December 2021, he signed an extension until December 2023.[8]