The move gives sweeping powers to security forces to arrest and detain suspects, and comes amid a tense standoff between the Supreme Court and the government.
The government has already suspended Parliament and ordered the army to resist any moves by the Supreme Court to impeach the President.
This is the second time Yameen has declared a state of emergency. He last took the step in November 2015 after an alleged attempt to assassinate him.
The court in a landmark decision ruled the trial of ex-President Mohamed Nasheed unconstitutional and ordered the release of nine MPs, which would see the opposition majority restored.
India has expressed concern over the recent political developments in the Maldives and asked its nationals to defer all non-essential travels to the Indian Ocean nation until further notice.
In an advisory, the Ministry of External Affairs (MEA) said Indian expatriates in Maldives are also alerted to the need for heightened security awareness, and urged to exercise due caution in public and avoid public gatherings.
"The prevailing political developments in Maldives and the resultant law and order situation is a matter of concern for the government. Indian nationals are, therefore, advised to defer all non-essential travels to Male and other atolls until further notice," the advisory said.
Reacting to the development, India had said it was imperative for "all organs" of the Maldivian government to abide by the country's Supreme Court order to release all political prisoners "in the spirit of democracy".
In a statement, the MEA had also said it was "closely monitoring" the evolving situation in the Maldives and also hoped that the safety and security of Indian expatriates in the island nation would be ensured by the Maldivian authorities under "all circumstances".
It said that as a close and friendly neighbour, India wishes to see a stable, peaceful and prosperous Maldives.
The island nation has been witnessing political unrest and street protests since Nasheed was convicted in 2015 on terror charges and sentenced to 13 years in jail.
There were reports of clashes between supporters of Nasheed and police in the capital city Male on Monday where hundreds of policemen were deployed to restore peace.
Nasheed was earlier granted asylum by the UK after he was authorised to seek medical treatment there amid mounting foreign pressure.
The leader, who is currently in Sri Lanka, welcomed the court order and said President Abdulla Yameen must resign in the wake of the ruling by the apex court.
(With inputs from agencies)