International arrivals in Sydney will be limited to 350 people per day under tighter COVID-19 restrictions to ensure returned travellers don't overwhelm the NSW health and hotel quarantine system.
Premier Gladys Berejiklian said the step was necessary to make sure the state stays in a strong position to prevent the virus spreading.
"Our number one priority is the health and safety of the people of NSW, and this new cap will help us protect our state from COVID-19," she said on Sunday.
"NSW is the gateway to Australia and it is important that passengers returning home do not overrun the capacity of NSW Health and hotel quarantine."
NSW on Sunday reported 18 new cases for the 24 hours to 8pm on Saturday, taking the number of active cases to 99, with one in intensive care.
The total number of cases associated with the Crossroads Hotel cluster is 45, while one of the new locally-acquired cases attended Holy Duck! restaurant in Chippendale on the evening of July 10.
Another case visited the Anytime Fitness Gym in Merrylands on 14 July from 9pm to 10:30 pm.
Anyone who attended the restaurant or the gym is being advised to immediately self-isolate for 14 days and get tested if they show symptoms.
The restaurant was closed on Saturday night and is being cleaned.
Five of the new cases were travellers returning from overseas and in hotel quarantine.
One worker at Northside Group Wentworthville Clinic, a private hospital in Sydney's west, has tested positive.
Three other staff members who were close contacts are in self-isolation.
The new airport cap is a reduction from a 450-person limit introduced on July 5 and will apply from 12.01am on Monday
Jobs Minister Stuart Ayres said Australians had been given plenty of time to return from overseas.
"It is incredibly important the volume of returning travellers does not undo the great work of the people of NSW," he said in a statement.
NSW Deputy Chief Health Officer Jeremy McAnulty has warned the state to stay vigilant.
"It wouldn't take much for us to be in Melbourne's situation. We need everyone's assistance," he said.
The Victorian government has made face masks or coverings mandatory for people who leave their homes in metropolitan Melbourne and the Mitchell Shire.
As students prepare to return to school on Monday, Transport and Roads Minister Andrew Constance said the 3300 extra services added to the state's public transport network in June would continue.
He urged people to avoid the early part of the morning peak and walk, cycle or drive where possible.
A new sanitising station for taxis and rideshare vehicles has also been fast-tracked at Prestons, in Sydney's southwest, following the spike in cases in the city's west.
Meanwhile, the retail, fast-food and warehouse workers union is urging people to not visit shops after being tested for coronavirus.
"Wait for your test results. Don't go until you know," the SDA's NSW/ACT secretary Bernie Smith said in a statement.
"Don't put the health of the workers in the store and other shoppers at risk."