The ceremony was held in the capital Dhaka on Thursday after the student revolt in the country succeeded in ousting Prime Minister Sheikh Hasina and her 15-year rule.
Yunus promised to uphold and protect the country's constitution.
Violence is our enemy, let us not create more enemies, said Yunus, who has lived in exile since 2008.
Yunus, who received the Nobel Peace Prize in 2006, has been hastily called upon to lead the country after the violent and deadly protests against the country's former regime.
Yunus leads a transitional government following an agreement between the military, leaders of civil society, and student activists. The latter led the unrest that began in discontent over a quota system that was said to favor supporters of former Prime Minister Hasina's party.
The plan is for the transitional government with Yunus at the helm to prepare for general elections. But nothing has been said about when they would be held.
