In March 2021, Mihăilă was called up for the first time to the [[Romania national football team|Romania senior team]] squad by head coach [[Mirel Rădoi]] for the [[2022 FIFA World Cup qualification – UEFA Group J|2022 FIFA World Cup qualifiers]] against [[North Macedonia national football team|North Macedonia]], [[Germany national football team|Germany]], and [[Armenia national football team|Armenia]]. On the 25th that month, he replaced injured [[Florinel Coman]] in the first half of the former game and netted in the 3–2 win at the [[Arena Națională]] in [[Bucharest]].<ref>{{cite web|url=https://www.digisport.ro/fotbal/echipa-nationala/valentin-mihaila-super-gol-marcat-la-debut-pentru-romania-macedonenii-n-au-scapat-de-ce-s-au-temut-1033494|title=Valentin Mihăilă, super-gol marcat la debut pentru România! Macedonenii n-au scăpat de ce s-au temut|trans-title=Valentin Mihăilă, super goal scored at the debut for Romania! The Macedonians could not escape from what they feared|publisher=Digi Sport|language=ro|date=25 March 2021|access-date=23 April 2021}}</ref>
On 19 June 2023, Mihăilă came on in the second half of a [[UEFA Euro 2024 qualifying Group I|Euro 2024 qualifier]] against [[Switzerland national football team|Switzerland]] and scored a late double to earn his team a 2–2 draw.<ref>{{cite web|url=https://www.digisport.ro/fotbal/echipa-nationala/valentin-mihaila-plateste-scump-dubla-de-poveste-din-elvetia-ce-a-patit-dupa-golul-doi-2453919|title=Valentin Mihăilă plătește scump "dubla" de poveste din Elveția! Ce a pățit după golul doi|trans-title=Mihăilă pays a heavy price after the amazing "double" in Switzerland! What happened after the second goal|publisher=Digi Sport|lang=ro|date=19 June 2023|accessdate=20 June 2023}}</ref> He was then meant to join up with the under-21 team for the [[2023 UEFA European Under-21 Championship|2023 European Championship]], but was ruled out after suffering an injury in the latter gamematch.<ref>{{cite web|url=https://www.digisport.ro/fotbal/echipa-nationala/ce-spune-emil-sandoi-despre-debutul-la-euro-2023-dupa-ce-mihaila-si-grameni-s-au-accidentat-avem-si-noi-o-experienta-2455053|title=Ce spune Emil Săndoi despre debutul la EURO 2023, după ce Mihăilă și Grameni s-au accidentat: "Avem și noi o experiență"|trans-title=What does Emil Săndoi say after Mihăilă and Grameni got injured: "We also have experience"|publisher=Digi Sport|lang=ro|date=20 June 2023|accessdate=20 June 2023}}</ref>
Romania secured their spot in the [[UEFA Euro 2024|Euro 2024]] by finishing first in their qualifying group, and on 7 June 2024 Mihăilă was selected as part of the final squad.<ref>{{cite web|url=https://www.frf.ro/nationale/masculin/echipa-nationala/lotul-romaniei-pentru-euro-2024/|title=Lotul României pentru EURO 2024|trans-title=Romania's squad for EURO 2024|publisher=[[Romanian Football Federation]]|lang=ro|date=7 June 2024|accessdate=5 July 2024}}</ref> He made three appearances, and only startingstarted in the 0–2 loss to [[Belgium national football team|Belgium]] on 22 June, as his country won its [[UEFA Euro 2024 Group E|group]] before being eliminated by the [[Netherlands national football team|Netherlands]] in the [[UEFA Euro 2024 knockout stage#Romania vs Netherlands|round of 16]].<ref>{{cite web|url=https://www.bbc.com/sport/football/live/c7204xy3zg1t|title=Romania 0–3 Netherlands: Donyell Malen and Cody Gakpo score as Dutch reach quarters|publisher=[[BBC]]|date=2 July 2024|accessdate=8 July 2024}}</ref>
