A memo circulated by the Foreign ministry on Thursday suggested that the diplomats affected had not reported for work over a period of time, some of them for as long as a couple of years.
The ministry said many of them were on leave that had not been authorized by the government.
According to the ministry, those axed were appointed to serve in the United States, UK, Kenya, Uganda and other African countries.
Following their decision to go AWOL, they had not responded to persuasion by the government for them to return to their posts, some of them in the capital Juba.
The mass firing of the diplomats comes on the heels of reducing the sizes of country's embassies abroad after it was realised that they were not sustainable given the biting economic difficulties blamed on conflict.