In his message, Haniyeh hailed Sheikholeslam's firm stances in accompanying the Palestinian nation.
Sheikholeslam passed away from the coronavirus on Thursday.
Foreign Minister Mohammad Javad Zarif, FM Spokesman Seyyed Abbas Mousavi and other Iranian officials extended condolences over his death.
Sheikholeslam was also an assistant to the parliament Speaker Ali Larijani for the International Affairs. He was a member of the Seventh Iranian Parliament, and also served as the Iranian ambassador to Syria. Sheikholeslam was elected deputy for international affairs at the World Forum for Proximity of Islamic Schools of Thought (WFPIST) in June 2018.