The 19-year-old came off the bench as the world champions beat Australia 2-0 in a friendly in China, replacing Nicolas Gonzalez with 16 minutes left.
The score was already 2-0 and that’s how the match finished, with Lionel Messi opening the scoring less than two minutes in with a superb goal.
It was not a game of great importance, but it will always be a special one for Garnacho who will hope it is the first of many caps for his country.
He wrote on Instagram: ‘And if this is just a dream never wake me up. Beautiful.’
Martinez, who was not with the Argentina squad as he continues to recover from injury, replied: ‘It looks good on you brother.’
Harry Maguire also added ‘Well deserved mate’ while the likes of Nicolas Otamendi, Rodrigo De Paul, Leandro Paredes chimed in with congratulations.
Before the match, Garnacho said it did not feel real to be playing alongside Messi, but was controlling his nerves ahead of his international debut.
‘I didn’t talk much with Messi,’ Garnacho told TyC Sports. ‘I went from watching him on TV all my life and now I have him here, it seems that it’s not real
‘I spoke with Lionel Scaloni here. He asked me if I was nervous and I told him I wasn’t. When I play I try to be me.
‘I’m a young guy but I don’t care about age, I try to play the way I know how.’
MORE : Chelsea consider using £45m star to beat Manchester United to Moises Caicedo transfer
MORE : Bayern Munich set to hijack Manchester United move for Kim Min-jae with personal terms close to being agreed
For more stories like this, check our sport page.
Follow Metro Sport for the latest news on
Facebook, Twitter and Instagram.
Stay connected with us on social media platform for instant update click here to join our Twitter, & Facebook
We are now on Telegram. Click here to join our channel (@TechiUpdate) and stay updated with the latest Technology headlines.
For all the latest Football News Click Here