Hirvonen's first win in Citroen colours came just weeks after his nine-time champion team-mate Sebastien Loeb's announcement that he would only contest a handful of rallies next year.
That put responsibility for continuing Citroen's run of title success on Hirvonen's shoulders, and he believes Italy proved he can handle that pressure.
"In a way, I feel like I've won my first ever rally. And for Citroen, we did," he said.
"We spoke with the team and with the mechanics before the start of the rally and decided this was going to be my first rally of 2013. So that's started well and now I want to keep it like this as well."
Hirvonen started the rally in a close battle with Loeb, then assumed a clear lead when his team-mate crashed on Friday morning. Ford drivers Petter Solberg and Jari-Matti Latvala also made mistakes while trying to give chase, meaning that by Saturday morning Hirvonen knew he just had to cruise to the finish with a big lead over M-Sport pair Evgeny Novikov and Ott Tanak.
"I knew this weekend we could do it, for sure," said Hirvonen, who clinched second in the drivers' championship in Italy. "You still have to finish all the stages and we just took it steady. I knew that we could go to the finish so slowly and just make sure we didn't make any mistakes, and we did, so I'm really happy."
Citroen team boss Yves Matton added that he was pleased Hirvonen had been able to get a win in 2012 after losing his Portugal victory to a technical infringement by the team.
"We felt that we owed them something after the Rally de Portugal and so it's immensely pleasing to see them win here," Matton said.
"This result wasn't served up for them on a plate. They had to adopt a very high level of performance from the very start and the other leading crews made mistakes when fighting with them for the lead.
"After winning the drivers' and manufacturers' titles at the Rallye de France, we have now added the final feather to our cap with the world championship runner-up spot for Mikko.
"There's only one more step for him to take in his career and we'll be trying very hard to help him achieve that in 2013."