On 14 June 2018, Martínez was named Granada CF manager, and achieved promotion to La Liga at the end of the season. The youngest manager of the 2019–20 campaign, his side enjoyed their best-ever league start after achieving 20 points in ten matches, bringing the "Nazaríes" to the top of the tournament for two weeks. As a result, he was rewarded with a one-year contract extension through 2021 on 14 November 2019.