The department said 1,525 people recovered from the disease and were discharged in the last 24 hours, aggregating to 27,10,288 leaving 40,260 active infections.
After recording nil Omicron cases over the past few days, 64 new cases were detected in the last 24 hours, aggregating to 185 till date, a medical bulletin said.
The last time when Tamil Nadu reported over 10,000 cases was in April 18, 2021 when it added 10,723 new cases.
Nearly half of the new Covid-19 cases reported today were contributed by Chennai with 5,098 infections, followed by Chengalpet 1,332.
As many as 14 districts reported new cases in triple digits, while Ariyalur recorded the least with four infections.
After witnessing a declining trend for several weeks, Tamil Nadu has been reporting sharp increase in new infections since last week. The state had recorded 8,981 new cases yesterday.
Those who tested positive today included 46 returnees from domestic and overseas locations.
A total of 1,39,253 samples were tested in the last 24 hours, pushing the cumulative number of specimens examined to 5,83,79,224.
On the status of the Omicron variant, the bulletin said of the 150 whole genomic sequencing samples sent earlier in the week, 74 results have been received and the rest are pending validation.
Of the results received 64 have been identified as Omicron and 10 as Delta variants, the bulletin said.
"Along with the 121 cases already declared, with the addition of 64 cases identified in the present set through whole genomic sequencing, the total Omicron cases in Tamil Nadu so far is 185", the bulletin said.
As many as 179 people have already been discharged leaving zero active cases, while six Omicron Cases have been cross notified to Kerala, Puducherry and Andhra Pradesh.
Meanwhile, Minister for Medical and Family Welfare Ma Subramanian said Chief Minister M K Stalin would formally launch the programme to administer booster doses to frontline and eligible senior citizens on January 10.
"Those people who have received both the vaccination doses against Covid before April 14, 2021 are eligible to receive the booster shots", he told reporters.
Tamil Nadu has been administering Covishield and Covaxin vaccines to a majority of beneficiaries, while some private health care facilities offered Sputnik.
"People who have received both doses of Covishield will be administered with Covishield, while those who received Covaxin will be administered Covaxin vaccine", he said.
The vaccination exercise was formally launched by Prime Minister Narendra Modi on January 16, 2021 countrywide.