The Argentine star has just over a year to run on his current deal and Sunderland are keen to tie him down to a new long-term deal.
Serie A newcomers Fiorentina are reported to be keen on Arca, but McCarthy is confident the South American ace will be going nowhere.
"Yes, contract talks are ongoing with Julio Arca, but to be honest, I have left all that to other people," McCarthy told the Sunday Sun.
"I like to get on with the football side of things - but, of course, I have been keeping up to date with everything that has been going on with Arca's situation.
"And everything is, I believe, very positive.
"Not in any way, shape or form has Julio ever suggested to me he wants to be anywhere else.
"He has been very much involved in pre-season and is very much involved in my future plans."
