[4] On 28 September 2012, while still a youth, he appeared with the first team in that year's Trofeo Santiago Bernabéu, coming on as a second-half substitute in an 8–0 rout of Millonarios.

[9] His maiden appearance in La Liga took place on 9 September, playing the full 90 minutes in a 5–0 defeat at Barcelona.

[15] On 7 September 2022, Hermoso scored a last-minute goal to open a 2–1 home defeat of Porto in the group phase of the UEFA Champions League; later, he committed a penalty that resulted in Mateus Uribe's equaliser, before Antoine Griezmann's winner.

[19] After playing for Spain at under-19 level, Hermoso was first called by the full side on 8 November 2018, for matches against Croatia and Bosnia and Herzegovina.

[20] He made his debut in the latter fixture, featuring the full 90 minutes in the 1–0 friendly win in Las Palmas.