The measure, passed today by a vote of 103 to 12, will allow citizens younger than 18 to vote in Britain for the first time.
It is a one-off change and will not apply to local elections or votes for the British Parliament.
Deputy First Minister Nicola Sturgeon said "young people have a significant stake in this country's future" and it was only right they should get a say.
The referendum on September 18, 2014, will ask Scots whether they want to remain part of the United Kingdom or become an independent country.