The former Blaugrana coach has attacked the 'Special One' with a flurry of criticism and claims the former Chelsea man runs into hiding when Barca come out to play
His assessment comes just 24 hours before the Blaugrana meet Manchester United at Wembley in the Champions League final, having beaten Madrid and Mourinho in the last four.
And Menotti, who won a World Cup with Argentina in 1978, feels the 'Special One' retreats into hiding when Barca appear.
"He got scared. You know what they say where I am from of Mourinho? That he is a chicken. And, to be more explicit, he shit himself," Menotti told press agencies DPA and Adnkronos.
"He left four attackers on the bench: [Emmanuel] Adebayor, [Gonzalo] Higuain, [Karim] Benzema and Kaka. How can you play without them?
"He played with three midfielders and just Cristiano Ronaldo up front [in the semi-finals]. He was scared. The 5-0 in la Liga killed him.
"That was his game and that's where he lost the Liga. Had he got a good result in the first game he would have been a God.
"But, not only did he lose, but it was the biggest loss in a Clasico. You can lose 2-1, but 5-0 was shameful."
On tomorrow's final, Menotti, who coached the Barca side which included Diego Maradona in 1984, added: "Manchester United are the only team who could create Barcelona problems."
Kick-off at Wembley is at 19:45 BST.