Martinez has just tied down young defender John Stones to a new five-year contract and is keen to reward the work done by McCarthy since his arrival from Wigan Athletic last summer.
The pair worked together at the DW Stadium for four years and the 23-year-old midfielder was one of the first players Martinez brought with him to Goodison Park.
After making his debut against Chelsea last September, McCarthy went on to make 34 appearances as Everton finished fifth in the Premier League table.
His continued progress has earned him further international recognition with the Republic of Ireland - he now has 23 caps - and Martinez insists a new deal is on the cards.
"It will be natural. James's contract is already performance related so the longer that he plays he gets a bigger reward," he told the Liverpool Echo.
"We will always be looking at rewarding players as they do well and James, clearly, is one of those.
"We always want to keep our young players important at the club and keep rewarding them. That will never change. That goes along with players who change their roles in the squad.
"We talk a lot about our young players and rightly so, but sometimes we forget that without that solid base of experienced lads behind them you don't go anywhere.
"We must remember that we have continuity too which is vital."
Tim Howard, Seamus Coleman and Ross Barkley have also signed new contracts at Goodison Park during the close-season.