The Buddhists authors have claimed King Kanishka as faithful to Buddhism. They claimed that like his great forerunner Ashoka, Kanishka in his later days being regretful of his past deeds, had embraced Buddhism for peace and consolation.
Asvaghosha virtually converted Kanishka into a Buddhist. Buddhism had a word of solace and peace for all the seekers of peace and tranquility. When Kanishka came along with his forces to Patliputra, he is said to have met the great Buddhist saint and scholar, Asvaghosha.
Kanishka was so much charmed by his personality, personal character, knowledge and practicability of his teachings that he accepted his religion and declared himself to be an Upasak like his great predecessor, Ashoka.
Kushan King Kanishka did a lot for the spread of Buddhism in his days. With the help of the Greek architect Agesiles, he erected a great relic tower at Peshawar which was admired by the whole Buddhist world. Kanishka had accepted the Mahayana creed of Buddhism as his state religion. He was the messanger of the Mahayana creed in Central Asia. It was this Mahayana creed so earnestly postulated by Kanishka, which eventually gave rise to a distinctive style of art, the Gandhara art. It is aptly opined – what Ashoka did for spread of Himayanism, Kanishka did the same for spread of Mahayanism, the sister wing of the same mother-tree, Buddhism.
It should also be remembered that though an devoted Buddhist by faith Kanishka remained tolerant to all other faiths prevalent in his days and his coins serve as the best evidence of this fact. The Kushan coins of Kanishka did not embrace any particular religion. The deities in Kushan coins indicate the various forms of faiths prevailing in his vast empire. Few coins depicting the figures of Shiva and Buddha have also been found.