Bahawal Khan, who also goes by the name Salahuddin Ayubi, has taken command of Mullah Nazir’s group, officials say.
Mullah Nazir died when two missiles struck his vehicle in the tribal area of South Waziristan on Wednesday.
He headed one of four major insurgent factions in Pakistan’s north-west and was a key figure in supplying fighters and support to the Afghan Taliban.
“Ayubi, whose real name is Bahawal Khan, was appointed as top commander of the group after Nazir’s funeral,” a Pakistani intelligence official told the AFP news agency.
Clerics and tribal elders had backed the appointment, a spokesman for the militant faction told the Express Tribune newspaper.
Bahawal Khan, said to be aged 34 and an illiterate former bus driver, is a long-time close associate of Mullah Nazir, the two men having fought together alongside the Taliban in Afghanistan before the 2001 US invasion.
BBC correspondents say Bilawal Khan is seen as hot-tempered, unlike his predecessor. But he is nevertheless expected to maintain the tribal consensus that Mullah Nazir had built up to keep his power base around the town of Wana largely peaceful.
In recent years there have been divisions among Taliban militant groups based in Pakistan’s tribal areas.
Mullah Nazir was one of the most high-profile insurgents killed by US drones. The faction he led straddles the border with Afghanistan.
For the Americans, he is a prized catch, as he headed one of the three major militant groups in the Waziristan region that focused their attacks on Nato-led troops in neighbouring Afghanistan, the BBC’s M Ilyas Khan in Islamabad says.
But his killing will be viewed by some as a dent in Pakistan’s preparations for the departure of foreign troops from Afghanistan, our correspondent adds.
Pakistan has worked hard to maintain a crucial strategic balance in Waziristan by forging peace with militant factions focused on the Afghan insurgency rather than on targets inside Pakistan.
Mullah Nazir had formed an alliance with the government and opposed the fourth main militant faction, the Tehreek-e-Taliban Pakistan (TTP), which has concentrated its fire inside Pakistan since 2007.
In recent months, the TTP has also carried out a number of attacks against the Wazir tribe in Wana, including a suicide bombing in November that injured Mullah Nazir.