Sanchez moved to Old Trafford in January from Arsenal. The Chilean has scored only once in nine appearances for United in all competitions.
Mourinho was asked whether Sanchez was happy at the club, following the 2-1 victory over Liverpool on Saturday.
“He’s fine. He’s happy that the team is getting results.
“Lately, he wasn’t happy when we lost matches with him but he’s a guy with great maturity, with great attitude and we couldn’t be happier,”Mourinho said.
United face Sevilla next in the Champions League on Tuesday, before taking on Brighton in the FA Cup quarter-final.