The victim was stabbed on Oxgangs Drive at lunchtime on Tuesday.
Police said they were following a “positive line of inquiry” and have urged witnesses to come forward.
Inspector David Ferguson of Drylaw police station said: “We’re carrying out inquiries after a male in his 20s was attacked and stabbed in Oxgangs Drive shortly before 1pm on Tuesday (July 12).
“Paramedics attended to the injured male and transferred him to the Royal Infirmary of Edinburgh where he remains in a serious condition.
“I’m satisfied that this is an isolated incident and we are currently pursuing a positive line of inquiry.
“However, I would urge anyone who has information that might assist with our ongoing investigation to contact us on 101 or the charity Crimestoppers anonymously on 0800 555 111.”