Unidentified gunmen opened fire on Mehsud in the village of Urmuz, in North Waziristan on Thursday.
Mehsud's death comes a week after the Pakistani Taliban, also known as Tehrik-e-Taliban Pakistan (TTP), announced that it was splitting into two separate groups. The deceased Taliban commander was a member of the dominant Mehsud faction.
Pakistani intelligence sources suspect that Mehsud was killed because of rivalries between the TTP factions.
No one has yet claimed responsibility for the attack.