He was declared elected unanimously by party's Central observer and former Minister Bandaru Dattatreya in the presence of senior leaders including Muralidhar Rao, party's state-in-charge and former state unit presidents L Ganesan and C P Radhakrishnan.
A former Union Minister, who was inducted in the A B Vajpayee-led government in 1999, Radhakrishnan's second term as BJP's state unit president will last for three years.
He had represented Nagercoil constituency in the Parliament.
After being declared elected, Radhakrishnan said he planned to hold a series of protests and agitations covering various areas including women's rights and agriculture.