Kiir last week fired his entire Cabinet. A government spokesman said an overhaul was long overdue.
South Sudan has struggled to maintain its footing in the two years since gaining independence from Sudan. A peace deal ensuring independence ended civil war in 2005, though both sides have continued to spar over border issues, rebel groups and oil revenue.
Kiir returned several ministers, including Petroleum Minister Stephen Dhiew Dau, to the administration. Government spokesman Barnaba Marial Benjamin was appointed Wednesday as foreign affairs minister in the new administration, the independent Sudan Tribune reports.
Former South Sudanese Vice President Riek Machar defended Kiir's decision to disband the government last week. The office of the vice president was left vacant, however, amid the power struggle.
Several ministries were combined in what Kiir was quoted as saying was a leaner administration.
"This downsizing will create synergies, allow budgets to flow to high priority development projects and also allow for better management by dedicated civil servants," he said.
Kiir this week pledged to ensure a state of national security during the administrative overhaul. The U.S. government, which was heavily involved in 2005 peace deal, said it was concerned about South Sudan's state of affairs.