Jundullah spokesman Fahad Marwat said on Wednesday that the visit took place this week in Pakistan's southwestern Baluchistan province.
He says the purpose of visit by the Islamic State group was to see how it could work to unite various Pakistani militant groups.
Jundullah is a branch of the Pakistani Taliban, or Tehrik-e-Taliban Pakistan as the group is known.
The TTP this week sacked its spokesman for announcing allegiance to the Islamic State group, which has captured large swaths of territory in Iraq and Syria and declared a self-styled caliphate, or Islamic empire, in the Middle East.