The goalkeeper spent almost the entire last season out of the team before playing the last five league games of the regular Championship campaign.
He played in the playoffs as well and was pivotal in getting Saints promoted to the Premier League.
With his contract expiring at the end of the month, the 34-year-old has been expected to move on from Southampton this summer.
He has even attracted interest from Saudi Arabia but it has been claimed that McCarthy is set to stay.
Russell Martin wants his experience in the squad as Saints prepare for life back in the top flight next season.
The goalkeeper will sign a new contract with the club and continue to be part of their set-up going forward.
It remains to be seen whether McCarthy starts the Premier League campaign as the Southampton number one next season.
