Cricket South Africa immediately cancelled Abbott's contract and said it was in the process of doing the same with one-day star Rilee Rossouw.
Both have Kolpak contracts with Hampshire which preclude them from playing for South Africa. Abbott has signed for four years and Rossouw for three.
The announcements came immediately after South Africa clinched a test series against Sri Lanka, winning the second test by 282 runs.
Abbott will not play in the third and final test in Johannesburg next week.
"It's a massive loss," said South African captain Faf du Plessis, who was unaware of Abbott's decision until the player told his teammates during the Cape Town test following a report from England about his impending move.
