The 71-year-old was found unconscious in her Los Angeles home on Tuesday afternoon.
A statement released on her website late on Friday said the singer was "resting comfortably". It is still not clear what Joni Mitchell is being treated for.
"We are encouraged by her progress and she continues to improve and get stronger each day," the statement said.
In December, Canadian-born Joni Mitchell told Billboard magazine that she had a rare skin condition, Morgellons disease, which prevented her from performing.