The Croatia international moved to the Serie A outfit from Dinamo Zagreb two years ago and has since made 62 league appearances in the Italian top flight.
Kovacic has netted seven goals in all competitions so far this season, but was shown a straight red card in the 1-1 draw with Juventus on Tuesday for a dangerous challenge on Stephan Lichtsteiner.
There was better news for Kovacic on Friday, however, as it was announced he had agreed terms on an extended deal.
"I thank the president and the club for the opportunity," Kovacic said.
"They are beautiful things and we hope to continue on this path. I am very happy for the renewal."
Head coach Roberto Mancini, meanwhile, believes the 20-year-old can go on to achieve great things at Inter.
"It's a great investment by Inter," he said. "I think he can improve a lot.
"He can become a great midfielder. We're happy to have him here."
'Obviously Messi is the best player in history and being compared to him means that you're doing things right, but I try to be myself': Barcelona star responds to comparisons with Argentine legend
'Darwin Nunez would be gold for Arsenal': Liverpool legend claims Gunners should have signed Uruguayan striker in January
