There was much talk that the pair did not get on when they worked together at Chelsea.
Mourinho sold Mata to Manchester United in 2014 for £37million in a move which surprised most Blues fans.
But two years later they were reunited when Mourinho took charge of the Red Devils.
The Spaniard has since been one of the first names on the team sheet and netted a brace in the 2-2 draw with Leicester last time out.
And now Mata says their relationship is as strong as ever and he is even hoping the Portuguese boss gets involved in his Common Goal charity, where sport stars donate one percent of their salary to charity.
“My relationship with Mourinho is good,” Mata told Marca.
“I’ve said it a thousand times already.
“We talk a lot, especially now at United, and he has a good relationship with the Spanish players.
“When we have time and the fixture list allows it, maybe in pre-season, we can talk about Common Goal.”
Mata is hoping to convince more players and managers to join his charity, which already boasts Juventus’ Giorgio Chellini and Bayern Munich’s Mats Hummels.
“Everything needs time and you have to be patient, but the welcome so far has been very, very good,” Mata added.
“Having recognised players signed up at the beginning, like [Giorgio] Chiellini, [Mats] Hummels, [Shinji] Kagawa and Veronica Boquete, is important for the project to have repercussions.
“But for me the story of a young boy who calls me and tells me that he likes Common Goal fills me with hope more because he doesn’t have a salary like ours and, despite everything, he wants to participate.”