Both leaders sat side by side in Saifai in the Etawah district, where Akhilesh Yadav gave his uncle the party flag, as SP candidate Dimple Yadav commanded a massivelead of more than two lakh votes in the Mainpuri Lok Sabha bypoll.
Later, they posted photographs of the event on Twitter.
Additionally, SP workers placed a flag on Shivpal Singh Yadav's car to symbolise the union of the two parties.
Shivpal Yadav and his nephew Akhilesh Yadav, known as "chacha-bhatija," came together despite ups and downs in their relationship to ensure Dimple Yadav victory in the byelection after SP founder Mulayam Singh Yadav's passing.
Samajwadi Party founder and patriarch Mulayam Singh Yadav passed away in October earlier this year at Gurugram-based Medanta Hospital after a prolonged illness. He was 82-year old.
(With inputs from agencies)