The 25-year-old is expected to finalise personal terms on a move to Selhurst Park and will become manager Alan Pardew’s third signing of the summer following the arrivals of Yohan Cabaye from Paris Saint-Germain and Patrick Bamford, on loan from Chelsea.
McCarthy joined QPR from Reading last summer but failed to dislodge regular ‘keeper Robert Green, making just four appearances for the club.
The former England Under-21 international will battle it out with Julian Speroni for the No 1 jersey at Palace.
Meanwhile, Sky sources also understand QPR are interested in signing Palace midfielder Adlene Guedioura.
The Algeria international midfielder had two loan spells with Watford last season, playing a part in their promotion to the Premier League.
Guedioura, who has a year left to run on his contract, joined Palace in 2013 but has struggled to establish himself as a first-team regular.