The 32-year-old had been in London over the past couple of days for a series of talks with the ECB regarding his England future.
It is believed that one of the major subjects for discussion was Pietersen's availability for next month's Test tour of India.
"Short & sweet London.. Bye bye," he wrote on Twitter. "Back to SA to the #CLT20.. Weather looks ok in Durbs."
The outcome of the talks has not yet been made public.