Sadanandar was born as the son of Sri Rangarayar of Thiruvidaimaruthur and was given the name Kasinathan. As he grew older, he worked as the Station Master at Thiruvidaimaruthur Railway Station.

With a deep inclination toward spirituality, he embraced renunciation and took voluntary retirement from his service. He learned Navakanda Yoga from Avadhuta Mauna Swamigal of Thiruvidaimaruthur, who accepted Sri Dattatreya Bhagavan as his Guru.

Later, Swamigal, known then as Kasinathan, traveled to Chennai, where he came to be known in the spiritual world as Sadanandar. During that time, he formed friendships and engaged in spiritual discussions with revered saints such as Chembakkam Ponnambala Swamigal, Kuyapettai Easur Sachidananda Swamigal, Vyasarpadi Karapathira Swamigal, Purasawalkam Veerasubbaiah Swamigal, and Mylai Kuzhandaivel Swamigal, who lived around the Chithiraikulam area of Mylapore.

Swamigal guided several of his disciples to attain Jeeva Samadhi, enabling them to achieve liberation (moksha).

He performed miracles for a police officer named Narayanasamy and accepted him as a disciple. Narayanasamy invited Sadananda Swamigal to his native place, Alappakkam, Perungalathur, Chennai, built a hut on his own land, and arranged for Swamigal to reside there.

At Alappakkam, Swamigal taught the people various forms of worship and yogic secrets. He performed many miracles for the community and served as a noble spiritual guide. The people revered him as both Guru and Divine, and his fame spread everywhere.

On January 16, 1922, on the auspicious Makam star day in the Tamil month of Thai, in the presence of his disciples Narayanasamy, Velusamy, Pachai Samy, and many devotees, Swamigal attained the divine state of Jeeva Samadhi.