The former Australian right-hand batter was rushed to hospital in late December amid a bout of meningitis, an infection and swelling of fluid and membranes around the brain and spinal cord.
Martyn, 54, had been placed in an induced coma and was fighting for life in a Gold Coast intensive care unit, but awoke last week and began talking again.
Former Test captain Michael Clarke was among those to travel to Queensland to visit Martyn, who has since returned home to continue his recovery.
"It's terrific and wonderful to know he's back home, and his family express their gratitude and thanks for all the support," former Test teammate Adam Gilchrist said on Kayo Sports during the fifth Ashes Test.
"The word from the medical staff was the ambulance officers who treated him as soon as they saw him could not have done it any more perfectly, which nipped the infection in the bud.
"He still has a bit of a journey to go, it was extreme, but great news."
Cricketer-turned-commentator Mark Waugh had held fears for Martyn, who had fallen ill suddenly on Boxing Day.
"It's almost a miracle really," Waugh said on Fox.
"He was looking in really bad shape when he was in the ICU, wasn't he?"
Darwin-born Martyn earned a Test debut at 21 replacing Dean Jones in the 1992-93 home series against West Indies, and was Western Australia's captain at 23.
He was player of the series the last time Australia won a series in India, topscoring in four of Australia's eight innings at the crease in the 2004 battle for the Border-Gavaskar Trophy.
His Test high score of 165 came against New Zealand in 2005, one of 13 centuries Martyn made in the baggy green. He averaged 46.37.
Martyn was among a handful of star Australian players to retire in the 2006-07 Ashes series, playing his final match at the Adelaide Oval that summer.
He also played 208 ODIs, averaging 40.8 and scoring an unbeaten 88 runs as Australia defeated India in the final of the 2003 World Cup.
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