The 35-year-old is in his eighth season with the Citizens and remains an important player at the Etihad Stadium, having already featured on nine occasions during the 2020-21 campaign.
A recent report claimed that Fernandinho was expecting to leave the club when his current deal expires next June, but Guardiola has suggested that an extension is a possibility.
"It is not necessary to say how important he is for all of us and me personally. The last game against Porto showed his incredible personality. We need Fernandinho a lot this season because we have just two holding midfielders and he knows the position perfectly," Guardiola told reporters.
"Last season he helped us a lot in a position where we didn't have much players with injuries so he is coming back to his position because we now have five central defenders.
"Whatever happens in the middle of the season or three-quarters of the way through or at the end of the season, him and the club are going to talk about it [a contract]."
Fernandinho, who has won three Premier League titles during his time at the Etihad Stadium, is believed to be wanted by City's sister club New York City FC, in addition to a number of Brazilian sides.