The midfielder, who arrived from Sporting CP for €40m plus €5m bonuses, played from the start in tonight's 2-1 victory away to Pescara.
“It's a very important win, so I am happy for the three points and with my first game in Serie A," Joao Mario told Inter Channel.
“This League is very different to Portugal and much more difficult. There are many quality sides and to get a result you need to put in the utmost effort to the end.
“It was my first match and I can't wait to play against Juventus at San Siro next week. We hope to win."