Prime Minister Hamza Abdi Barre said in a televised address that Robow, who once had a $5 million bounty on his head before he split from al-Shabaab in 2013, will become minister of religious affairs.
He previously left the terrorist group after disagreements with its leader Ahmed Abdi Godan in 2013. Godan was killed in an American drone strike the following year.
Analysts told CNN that Robow was one of the most senior al-Shabaab members to leave the sect. However, he failed to convince many militants to surrender with him to the Somali government, said Stig Jarle Hansen, author of Al-Shabaab in Somalia: The History and Ideology of a Militant Islamist Group.
“Robow is one of the main early members of Al-Shabaab and one of the main [members] Afghan veterans returning to Somalia,” Hansen told CNN.
Al-Shabaab fought to overthrow the Somali government and establish a rule based on a strict interpretation of Islamic Sharia law.
Earlier in May, the sect took over a major African Union military base in Mogadishu, killing several peacekeepers.
Al-Shabaab has long been designated by the United States as a foreign terrorist organization.