The night of the colonels' coup, on April 21, 1967, Konstantinos Mitsotakis was among the first arrested and transferred with other political leaders to the Armored Center of Goudi. From there, was next led to Pikermi and then was placed under house arrest, for six months. During that time, he had no outing rights and his communication with any person was impossible and also dangerous.
Mitsotakis was the first to propose the formation of a national unity government under Constantine Karamanlis to smoothly move the country towards democracy, during a statement of his about the constitution and the holding of a "referendum" by the junta in 1968. On the occasion of this statement, he was pursued by the junta and was forced to flee abroad. On August 15, 1968 he secretly began his journey by boat from Rafina, crossed the Aegean Sea and arrived in Cesme, Turkey. Then, he was launched in Izmir. There from he went to Paris where he would remain in exile for the next six years. The Dictatorship blackmailed his return by putting his family under house arrest and refusing to allow its exit from Greece, until June 1969 when it was granted a permission to leave. The Mitsotakis family is united again in Paris, where it remains in exile, until the fall of 1973.
Konstantinos Mitsotakis cooperated abroad with all the resistance forces and was the closest collaborator of Karamanlis, in Paris. With the lifting of Martial Law, in October 1973, he returned to Greece where he was imprisoned again by the Ioannidis regime, in Chania prisons, in July 1974. The restoration of democracy and the return of Karamanlis in Greece, found him again in prison.