Alderete has represented Paraguay at U17, U20 and U23 level. He won eight caps for the U17 team at the 2013 South American Under-17 Football Championship in Argentina, prior to winning seven caps for the U20s at the 2015 South American Youth Football Championship in Uruguay. In May 2016, Alderete played four times for the U23s at the 2016 Toulon Tournament in France, scoring one goal in a win over Guinea on 19 May. He was called up to train with Juan Carlos Osorio's senior squad in 2018. He made his debut for them on 20 November 2018 in a friendly against South Africa; as a starter.
