The former England boss, who played and became an assistant boss at Derby, heads into the job following a coaching stint with Queens Park Rangers.
"I've always followed Derby County because I played, I was an assistant [here]," McClaren said in a press conference. "It was one of them you always think in the back of your head, 'I'd love to manage that club one day'.
"The opportunity came very quickly, I had no hesitation. To come here, I'm thrilled, excited, I think its a big challenge ahead. We're here for two and a half years and we want to make developments, fill this stadium, get the fans excited. They're the most important people at this football club."
McClaren will watch tonight's clash against Ipswich Town from the stands.