Over the past 24 hours, the Islamic republic officially recorded 17,430 cases of infection, health ministry spokesperson Sima Sadat Lari said.
The figure eclipses a previous peak in late November of 14,051 daily cases, and brings Iran's total number of cases to 1,963,394.
Iran also recorded 174 additional virus deaths, Lari said, bringing the total to 63,506.
Lari warned the population of a "major increase in infections" to come.
The Islamic republic is battling the Middle East's deadliest coronavirus outbreak, and case numbers have risen following a surge in trips during the Iranian new year holidays in recent weeks.
Iran is facing "one of the most severe waves" of its coronavirus outbreak, Health Minister Saeed Namaki had said Monday.
"We've now lost the reins" of the virus, he said.
Some officials, including Namaki, have admitted in the past that the virus numbers are likely higher than official figures.
Authorities had warned of a concerning rise in the spread of the more contagious British variant of the disease and of a "fourth wave" prior to the holidays.
Dozens of towns and cities including the capital Tehran are classified as "red", the highest rating on the country's coronavirus risk scale, requiring all non-essential businesses to close.
Iran has avoided imposing a full lockdown on its population of 82 million since the pandemic started.
Instead, it has resorted to limited and shifting measures, such as temporary bans on travelling or businesses.
Authorities announced overnight Monday to Tuesday the arrival of more than 700,000 doses of the AstraZeneca/Oxford vaccine, its first delivery via the Covax vaccine-sharing programme.
Iran began its vaccination campaign in February, but it has progressed more slowly than authorities had hoped.
Agencies contributed to this report.