The Portuguese coach, who is believed to be ready to put pen to paper on a new contract at the Bernabeu, was poached by the Football Association after McClaren failed to qualify for Euro 2008.
"I was on the verge of coaching the English national team in 2007," Mourinho told ABC newspaper. "I thought about it carefully and I said 'no' because I knew that within two months I would be unhappy.
"National team coaching is not a life for me right now, with a game once a month, waiting two years for a serious competition."
Real became La Liga champions under Mourinho this season.