Victor Calvagna, president of Puttinu Cares, is brain dead, and treatment is being withdrawn to let nature take its course, his wife said in a Facebook post on Thursday evening.
Calvagna, 63, a much-loved paediatric cancer specialist, was hit by a car in Qawra two days ago in an accident that drew an outpouring of grief across the country.
His wife Carmen said MRI tests were showing that he is brain dead.
"They will stop all treatment and let nature take its course. Let's pray for the good Lord to welcome him," she wrote.
Calvagna was one of the founders of Puttinu Cares, a charity which has set up homes in London to care for young Maltese cancer patients needing treatment in the UK, and their families.