Martínez Munuera was selected as an additional assistant referee for the 2017 UEFA European Under-21 Championship in Poland. In 2018, he was chosen as a referee for the 2018 UEFA European Under-19 Championship in Finland, where he officiated three matches including the final between Italy and Portugal. The following year, he served as a video assistant referee at both the 2019 FIFA U-20 World Cup in Poland and the 2019 FIFA Club World Cup in Qatar, including the final of the latter between English side Liverpool and Brazilian side Flamengo. He also worked as the assistant VAR in the final match of the 2019 UEFA Nations League Finals between Portugal and the Netherlands. On 17 April 2021, he officiated the 2021 Copa del Rey Final between Athletic Bilbao and Barcelona.