The 23-year-old, who has previously played for Argentina's under-20 side, was named in Alejandro Sabella's 23-man line-up for the friendly against Saudi Arabia in Riyadh on November 14.
Di Santo will be in exulted company, with Lionel Messi, Gonzalo Higuain and Sergio Aguero the other three strikers, and Martinez is understandably proud of his player.
The Wigan boss said: "To get an Argentina cap is a huge achievement. We should never forget the players that he's going to have in that squad. For us it's a great feeling of pride. We're all very, very proud of what Franco has achieved.
"It's been a target of his and it's an incredible journey he's been on. He arrived here as a young man with great potential, now he's a proper footballer, a top player.
"You look at the squad and you've got players from Barcelona, Real Madrid, Manchester City and Wigan in that forward line, and that's a real compliment for everybody at the football club but especially Franco."
Di Santo joined the Latics in the summer of 2010 from Chelsea having never scored for the London side and having managed only a single goal in English football, on loan at Blackburn.
It took him until April 2011 to get off the mark for Wigan but last season he was the club's leading scorer, albeit only with seven goals, while he has begun this campaign in promising fashion.
Di Santo has already netted three times in the Barclays Premier League and has formed a good partnership with new recruit Arouna Kone.
Martinez said: "We always had a huge belief in Franco, we always saw his potential. The chairman made a massive investment in him and since then his application and his desire to fulfil his potential has been very important.
"Now I do feel he's reached a very good level but there's still a long way to go, and he knows that.
"We're all very excited about what the next level will bring because he's ready to be an important player in the Argentina squad and that's the next step for him."
Di Santo should return to the side for the Barclays Premier League trip to Tottenham on Saturday after being rested for Tuesday's Capital One Cup fourth-round clash against Bradford.
The Latics were big favourites against a team from the bottom tier of the Football League but they were knocked out on penalties after a goalless draw at the DW Stadium.
Martinez made nine changes to his side from last weekend's 2-1 win over West Ham, giving starts to the likes of Callum McManaman, Fraser Fyvie and Daniel Redmond.
And he feels the result was an acceptable price to pay for blooding young players at first-team level.
"It will have a very positive effect because the youngsters that were involved will learn from that" said the Spaniard.
"We scored eight goals in two games in the competition and were very clinical, and then we played against a team at home and we created more chances than the other two games together and for one reason or another we couldn't hit the back of the net.
"We didn't progress in the tie for the right reasons and I saw youngsters taking responsibility, showing very good things.
"If you cannot score from the opportunities we created, we wouldn't be able to win the competition, so you need to accept you need to get better and stronger as a squad.
"We need to develop our young talent and we need to do that more often and in a bigger number, and to do that we'll have to sacrifice some results."