The guitarist surprised the students of Belvedere College by presenting a cheque to them on the 31st Annual Belvedere College Sleepout.
The students started the sleep-out yesterday and will finish tomorrow on Dublin's O'Connell street and College Green.
The amount of money donated by The Edge remains undisclosed.The star has been enjoying some down time in Dublin ahead of Christmas.
Keith Duffy's son Jay, a budding actor, has been sleeping out at the GPO with the schoolboys to raise funds.Jay has been using his celebrity connections to raise awareness.
Kodaline, Ryan Tubridy, Gay Byrne and Brendan Gleeson all showed their support for the sleep-out.One Direction's Niall Horan tweeted his support, causing the site to crash temporarily.
The boys are hoping to beat last year's record and raise over €143k for Focus Ireland, the Peter McVerry Trust and Home Again.
To donate online, see www.sleepoutdublin.ie