Senate President Bukola Saraki, Samuel Ortom, governor of Benue state, and Aminu Tambuwal, governor of Sokoto, attended the national executive committee (NEC) meeting of the Peoples Democratic Party in Abuja on Thursday.
The top politicians are among key members of the All Progressives Congress (APC) who defected to the PDP recently.
Although the ruling party has dismissed reports that their defection would affect its chances next year, some political experts have described it as a big blow on APC.
Ortom, Tambuwal and Saraki were all members of the nPDP bloc which teamed up with the APC in the buildup to the 2015 elections.
The alliance contributed significantly to the victory of APC in 2015.