The grim milestone represents a significant spike from the previous single-day death toll record of 279.
"In recent days, we have witnessed an unprecedented increase in mortality from the disease," Health Ministry spokeswoman Sima Sadat Lari said in televised remarks.
Lari also said that 4,251 new cases were identified from Sunday to Monday, bringing the country's total number of identified cases to 534,631.
"The current situation is the result of neglecting to comply with health protocols, reduced use of masks and dangerous social behavior in recent weeks," Lari said.
The spokeswoman said that more than 431,000 patients have recovered from the coronavirus infection so far or have been discharged from hospitals across Iran.
Among those undergoing treatment in medical centers at present, 4,771 coronavirus patients have critical health conditions because of more severe infection, Lari added.
On Sunday, she warned that the virus prevalence rate is on the rise in the country.
She said all but one of Iran’s 31 provinces have been classified as red zones or are in the alarming situation.
Lari also said that the only province in the country that is in the yellow situation is Sistan and Baluchestan Province.
Iran has opted for a color-coded system of white for low-risk parts of the country, yellow for medium-risk and red for high-risk areas.
Iran has been struggling with the coronavirus since announcing its first cases in February.
In recent weeks, Iran has seen daily death tolls spike to their highest-ever levels.
Last week, as the daily death toll hit the record for three times, authorities announced tighter restrictions for the hard-hit Tehran Province.
Recently reopened universities and schools, as well as libraries, mosques, cinemas, museums and beauty salons, shut down. In the past week, the government mandated that all Tehran residents wear face masks outdoors and in public places, warning violators would be fined. Officials promised those who tested positive would be closely tracked.
Authorities on Saturday extended the restrictions imposed in the province for the second time to limit the spread of the virus.
IRNA, Reuters and AFP contributed to this story.