At a glittering ceremony, the 67-year-old leader was administered the oath of office and secrecy by Governor K Rosaiah with the party faithful raising slogans in her favour. Twenty eight ministers were also sworn in.
Her return to power comes as a shot in the arm for the AIADMK ahead of Assembly elections next year.
Shouts of 'Puratchi Thalaivi Vazhga' (Long live the revolutionary leader) echoed across the Madras University centenary auditorium as Jayalalithaa took the oath in the name of God in Tamil.
Jayalalithaa was disqualified following her conviction in the Rs 66.66 crore disproportionate assets case by a trial court in Bengaluru on September 27. The Karnataka High Court had subsequently acquitted her of the charges on May 11.
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The ceremony was witnessed by a galaxy of dignitaries including superstar Rajinikanth, actor Sarathkumar, Union Minister Pon Radhakrishnan and AIADMK leader and Lok Sabha Deputy Speaker M Thambidurai.
Jayalalithaa retained almost the entire previous cabinet.
Incidentally, Ministers were sworn-in in two batches of 14 each, making the formal event a short one. They, including outgoing chief minister O Panneerselvam, were seen reverentially greeting their leader with folded hands after taking over.
The swearing-in was also attended by actors Sivakumar and his son Karthi, industry captains like N Srinivasan of India Cements and some religious heads.
This time, the Ministers and other supporters were all smiles in stark contrast to that of the low-key swearing-in ceremony on September 29, when Panneerselvam became the stop-gap CM, two days after Jayalalithaa's conviction.