The Spanish champions confirmed on Tuesday they had reached an agreement for Martino to take over the reins at the Nou Camp on a two-year deal.
The 50-year-old former Paraguay boss succeeds Tito Vilanova, who stepped down from the role on Friday after one season in charge as he continues his battle with cancer.
Both Martino and Messi are from the Rosario region of Argentina and the four-time Ballon d'Or winner has spoken in glowing terms about his compatriot in the past.
And Martino reckons Messi put in a good word for him with the Barcelona hierarchy.
"I don't know the details of the situation, (but) I have no doubts that Messi spoke with the club directors. I'm sure that Jorge (Messi's father) and Leo have had some weight in this decision," Martino said in a press conference in Rosario this evening.
"They've given their opinion and we've arrived at this end.
"How much weight their opinions held in the decision I don't know but I'm grateful."
He added: "To coach Barca us an extremely important opportunity. I'm very grateful that Barcelona have gone for me and my coaching team."
A host of managers were linked to the vacant position with the Spanish champions, including Luis Enrique, Andre Villas-Boas, Marcelo Bielsa, Michael Laudrup and Guus Hiddink, who yesterday resigned as coach of Anzhi Makhachkala.
However, Martino emerged as the favourite over the weekend and the former Argentina midfielder was today confirmed as Barca's new boss, subject to the drafting and signing of his contract with the Catalan club.
Martino, who led Newell's Old Boys to the Argentinian Clausura title last season but recently severed ties with the club, admits Barca's approach had caught him off guard.
"Of course it took me by surprise," he said.
"I had virtually prepared myself to take a break and wait for the right job opportunity to arise."
Looking ahead to his new life in Spain, Martino said: "It's a big challenge to join a club of this magnitude and to try and do a good job. As with every big club, I want our team to be serious candidates to win every competition.
"We understand the institution that were going to, its history, how they have a defined style, and we are the ones who must insert ourselves into that and see how we can make our contribution to a squad that is very good and which has done great things in recent years.
"I don't know when I'll take charge of my first match, first I must adapt and finish with the contractual matters."
Martino also denied there will be an option in his contract which would free him to take over national team duties with Argentina, saying: "I don't put clauses in my contracts."
Martino has a reputation as an attack-minded coach and Barca midfielder Andres Iniesta believes he will fit in with the club's football philosophy.
"Whatever the club decide is the best for Barca. I think he will fit in with our model," Iniesta told Marca while at a promotional event today
"If the club have decided on him, then he's the ideal coach for us."
While Martino spent a short spell with Spanish side Tenerife as a player, he has never before coached a European side but he has enjoyed success during a 15-year career as a manager in South America.
At club level, aside from last season's title with Newell's, he also won various trophies with Club Libertad and Cerro Porteno in Paraguay.
He also enjoyed a hugely successful four-year spell in charge of that Paraguayan national team, guiding them to the quarter-finals of the 2010 World Cup and the final of the 2011 Copa America.
Paraguay had never before gone beyond the last 16 of the World Cup while the last time they made the Copa America final was in 1979.
Martino, who as a player represented local club Newell's in three different spells while also turning out for Lanus in his homeland, Barcelona SC in Ecuador and O'Higgins in Chile, becomes the fourth Argentinian to coach Barca, following in the footsteps of Helenio Herrera, Roque Olsen and Cesar Luis Menotti.