The changes came amid hyperinflation and the depreciation of the South Sudanese pound, the country's local currency.
South Sudan President Salva Kiir on Friday evening sacked the Minister for Finance and Planning Bak Barnaba Chol, replacing him with Daniel Daniel Chuong, an engineer.
In a presidential decree issued in Juba, the capital of South Sudan, Kiir did not give any reason for the dismissal of the Finance minister.
The new Finance minister previously served as the former minister of Petroleum and was until his appointment the technical adviser in the petroleum ministry.
The changes came amid hyperinflation and the depreciation of the South Sudanese pound (SSP), the country's local currency.
The SSP fell to a record low of 1,800 units against the US dollar, compared to 1,100 units to the greenback three months ago.
The country is currently struggling to increase daily oil production from the current 150,000 barrels a day to 175,000 barrels per day to secure hard currency to stabilise the economy.