The South Asian island country had plunged into instability after President Maithripala Sirisena replaced Wickremesinghe with Mahinda Rajapaksa, who was then twice sacked by parliament. Rajapaksa resigned on December 15 as a government shutdown loomed.
"He (Wickremesinghe) will take oath at an auspicious time today morning," Rajitha Senaratne, a cabinet spokesman under Wickremesinghe's former government, told Reuters.
An official at the president's office confirmed Wickremesinghe's oath taking.