Yesterday's photo is the first sight of the 74-year-old since he left in early May. Buhari also spent a month and a half in London earlier this year and said he had never been so sick in his life.
The absences and lack of information have caused tensions in Africa's most populous nation.
The new photo shows Buhari sitting and smiling with a number of governors. His office says he will return "as soon as his doctors give the go-ahead."