A 20:00-06:00 curfew has been announced in the island city and will remain in effect for at least 72 hours.
Traffic restrictions are in place during the curfew, while businesses in the busy South Beach area must close.
Miami Beach Mayor Dan Gelber said thousands of tourists had brought "chaos and disorder" to the city.
"It feels like a rock concert, wall-to-wall people over blocks and blocks," Mr Gelber told CNN. "If you're coming here to go crazy, go somewhere else."
Spring break is a holiday period for schools and universities in the US that usually takes place in March or April. It attracts thousands of students to Florida and other warm weather destinations around the country.
Officials warned tourists to "vacation responsibly or be arrested" prior to the holiday period, and a county-wide midnight coronavirus curfew was already in place due to the pandemic.
But the Miami Beach area was thronged with revellers over the weekend, and many did not appear to be wearing masks or socially distancing.
One city official described South Beach, which includes the world famous Ocean Drive, as being "overwhelmed" by crowds on Saturday.
"You couldn't see pavement and you couldn't see grass," city manager Raul Aguila said.
He added that the emergency measures were "necessary not only to protect our residents but our visitors, including our spring breakers who we want to keep safe".
On Sunday, Miami Beach police told CNN they had arrested at least a dozen people after the curfew had come into force.
Until the measures are lifted, police will prevent pedestrians or vehicles entering the South Beach area's main party strips.
Mr Aguila told the Miami Herald newspaper that he has recommended keeping the emergency measures in place until April 12.
But the emergency orders will expire on Tuesday evening unless they are extended by local authorities.
Florida continues to be a coronavirus hotspot in the US. The state has recorded nearly two million of the country's 29 million infections since the pandemic began.
The latest data from the US Centers for Disease Control and Prevention (CDC) shows Florida has recorded about 4,300 new infections a day on average over the past week.