"This increase in numbers is in fact a reflection of our overall performance, both in terms of reopening and in compliance with health protocols," Health Ministry spokeswoman Sima Sadat Lari said at a news conference.
The previous record daily toll of 158 deaths was reported by health authorities in early April.
Official figures have shown an upward trajectory in new confirmed cases since early May, when Iran hit a near two-month low in daily recorded infections.
Iran reported its first COVID-19 cases on February 19 and it has since struggled to contain the outbreak, the deadliest in West Asia.
Lari announced an additional 2,536 new cases on Monday, bringing the total to 225,205. The overall official death toll is now at 10,670
She also put the number of those who have recovered from the infection at 186,180.
Now 3,037 other COVID-19 patients are in critical condition and being treated in intensive care units, the spokeswoman said.
Iran has refrained from enforcing full lockdowns to stop the pandemic's spread, and the use of masks and protective equipment has been optional in most areas.
Iran closed schools, canceled public events and banned movement between its 31 provinces in March, but the government progressively lifted restrictions from April to try to reopen economy.
Iran's Leader Ayatollah Seyyed Ali Khamenei said on Saturday that "momentum and effort have waned among some of the people and authorities" to combat the virus, warning the country's economic problems would worsen if the disease spreads unchecked.
Authorities launched a campaign over the weekend to encourage people to wear masks and decreed mandatory mask-wearing "in covered spaces where there are gatherings" from Saturday, the beginning of the week in Iran.
Zanjan in northwestern Iran has already reimposed restrictive measures for two weeks, its governor said in a televised interview.
It followed a "certain indifference from Zanjan residents and as the number of our (virus) deaths picked up again in recent weeks," said Alireza Asgari.
The limitations include closing wedding halls and a ban on funeral events held at mosques, as they can lead to large gatherings, he added.
The increasing virus caseload has seen some previously unscathed provinces classified as "red" – the highest level on Iran's color-coded risk scale – with authorities allowing them to reimpose restrictive measures if required.
According to Lari, the provinces of Khuzestan, Hormuzgan, Kurdestan, Kermanshah, Bushehr, West and East Azarbaijan, and Khorasan Razavi are classified as "red".
The provinces of Ilam, Lorestan, and Golestan are on alert, she added.
President Hassan Rouhani said Sunday mask-wearing will become mandatory in certain areas as he allowed virus-hit provinces to reimpose restrictions to contain coronavirus spread.
Mask-wearing would be "obligatory in covered spaces where there are gatherings", he said during a televised meeting of the anti-virus taskforce.
According to him, the measure would come into force as of next Sunday, continue until July 22 and would be extended if necessary.
Rouhani said the Health Ministry had devised "a clear list" of the types of spaces and gatherings deemed high-risk.
Rouhani said Iran would have to live with the virus for the "long haul".
AFP and IRNA contributed to this story.