Unknown as of December 2015, but when it is eventually released on DVD it will be added to Netflix.
As of December 2015, Seasons One through Four are streaming on Netflix.
Season Four debuted in September 2014 & Season Three began streaming on Netflix in August 2014.
When does once upon a timesOnce Upon a Time Season 4 come on Netflix
As of January 2015, Season 3 of Once Upon a Time is currently available on Netflix.
Once the whole season is over
As of January 2015, Once Upon a Time is currently available on Netflix.
Netflix is always 1 season behind the current season that is on TV. So to get season 3 on Netflix, you have to wait until season 4 is on TV.
As of September 2014 it is currently streaming & available for rental on Netflix.
As of January 2016, Seasons 1 through 4 are streaming on Netflix.
Next month in may 2013
It will come soon, once they finish dubbing it in English.