| MD | Players | Club | Nationality | DOB | A(D) |
|---|---|---|---|---|---|
| 18-Feb-2018 |  Rio Dyer | Gwent Dragons | Wales | 21-Dec-1999 | 18(60) |
| 05-Jan-2018 | Taine Basham | Gwent Dragons | Wales | 02-Nov-1999 | 18(65) |
| 16-Feb-2018 | Dewi Cross | Ospreys | Wales | 06-Dec-1999 | 18(73) |
| 24-Feb-2018 |  Corey Baldwin | Scarlets | Wales | 13-Oct-1999 | 18(135) |
| 02-Dec-2017 | Will Jones | Ospreys | Wales | 03-Dec-1998 | 18(365) |
| 09-Sep-2017 | Giovanni D'Onofrio | Zebre | Italy | 25-Aug-1998 | 19(15) |
| 09-Mar-2018 | Ryan Conbeer | Scarlets | Wales | 05-Feb-1999 | 19(32) |
| 01-Dec-2017 | Dan Babos | Gwent Dragons | Wales | 17-Oct-1998 | 19(45) |
| 16-Sep-2017 | Matt Fagerson | Glasgow Warriors | Scotland | 16-Jul-1998 | 19(62) |
| 06-Apr-2018 |  Matt Dalton | Ulster | Ireland | 16-Nov-1998 | 19(141) |
| 22-Sep-2017 | Max Williams | Gwent Dragons | Wales | 02-Apr-1998 | 19(173) |
| 06-Apr-2018 | Tom O'Toole | Ulster | Ireland | 23-Sep-1998 | 19(195) |
| 02-Sep-2017 | Keelan Giles | Ospreys | Wales | 29-Jan-1998 | 19(216) |
| 21-Apr-2018 | Dylan Moss | Ospreys | Wales | 08-Sep-1998 | 19(225) |
| 26-Nov-2017 | Ioan Nicholas | Scarlets | Wales | 03-Apr-1998 | 19(237) |
| 22-Sep-2017 | Owain Leonard | Gwent Dragons | Wales | 24-Dec-1997 | 19(272) |
| 27-Oct-2017 | Jared Rosser | Gwent Dragons | Wales | 31-Dec-1997 | 19(300) |
| 06-Jan-2018 | Jonny Stewart | Ulster | Ireland | 20-Feb-1998 | 19(320) |
| 24-Nov-2017 |  Owen Lane | Cardiff Blues | Wales | 20-Dec-1997 | 19(339) |
| 24-Feb-2018 | Reuben Morgan-Williams | Ospreys | Wales | 02-Feb-1998 | 20(22) |
| 03-Nov-2017 | Aaron Wainwright | Gwent Dragons | Wales | 25-Sep-1997 | 20(39) |
| 03-Nov-2017 | Will Talbot-Davies | Gwent Dragons | Wales | 11-Sep-1997 | 20(53) |
| 08-Sep-2017 | Kieron Assiratti | Cardiff Blues | Wales | 30-Jun-1997 | 20(70) |
| 23-Feb-2018 |  Ciaran Frawley | Leinster | Ireland | 04-Dec-1997 | 20(81) |
| 02-Sep-2017 | Jordan Larmour | Leinster | Ireland | 10-Jun-1997 | 20(84) |
| 24-Nov-2017 | Ellis Shipp | Gwent Dragons | Wales | 14-Aug-1997 | 20(102) |
| 03-Nov-2017 | Andrea Bronzini | Benetton Treviso | Italy | 29-Jun-1997 | 20(127) |
| 01-Jan-2018 |  Calvin Nash | Munster | Ireland | 08-Aug-1997 | 20(146) |
| 02-Sep-2017 | Yaw Penxe | Southern Kings | South Africa | 03-Apr-1997 | 20(152) |
| 09-Feb-2018 | Marcus Rea | Ulster | Ireland | 08-Sep-1997 | 20(154) |
| 06-Jan-2018 | Cillian Gallagher | Connacht | Ireland | 23-Jul-1997 | 20(167) |
| 28-Oct-2017 |  Luke Crosbie | Edinburgh Rugby | Scotland | 22-Apr-1997 | 20(189) |
| 02-Sep-2017 | Giovanni Licata | Zebre | Italy | 18-Feb-1997 | 20(196) |
| 01-Sep-2017 | Blair Kinghorn | Edinburgh Rugby | Scotland | 18-Jan-1997 | 20(226) |
| 09-Feb-2018 | Darcy Graham | Edinburgh Rugby | Scotland | 21-Jun-1997 | 20(233) |
| 22-Sep-2017 | George Gasson | Gwent Dragons | Wales | 15-Jan-1997 | 20(250) |
| 23-Mar-2018 | Connor Edwards | Gwent Dragons | Wales | 28-Jun-1997 | 20(268) |
| 02-Sep-2017 | Scott Cummings | Glasgow Warriors | Scotland | 03-Dec-1996 | 20(273) |
| 16-Sep-2017 | Junior Pokomela | Cheetahs | South Africa | 10-Dec-1996 | 20(280) |
| 02-Sep-2017 | Leon Brown | Gwent Dragons | Wales | 26-Oct-1996 | 20(311) |
| 31-Dec-2017 | Arwel Robson | Gwent Dragons | Wales | 21-Feb-1997 | 20(313) |
| 21-Apr-2018 | Matthew Aubrey | Ospreys | Wales | 04-Jun-1997 | 20(321) |
| 02-Sep-2017 | Matthew Smith | Glasgow Warriors | Scotland | 05-Oct-1996 | 20(332) |
| 09-Feb-2018 | Jonny McPhillips | Ulster | Ireland | 13-Mar-1997 | 20(333) |
| 02-Sep-2017 | Max Deegan | Leinster | Ireland | 01-Oct-1996 | 20(336) |
| 29-Sep-2017 | Josh Macleod | Scarlets | Wales | 27-Oct-1996 | 20(337) |
| 01-Jan-2018 | Robert Lyttle | Ulster | Ireland | 28-Jan-1997 | 20(338) |
| 01-Sep-2017 | Sean O'Connor | Munster | Ireland | 22-Aug-1996 | 21(10) |
| 27-Oct-2017 | Owen Watkin | Ospreys | Wales | 12-Oct-1996 | 21(15) |
| 01-Sep-2017 | Jamie Ritchie | Edinburgh Rugby | Scotland | 16-Aug-1996 | 21(16) |
MD = Match date,
DOB = Date of birth,
A(D) = Age(days).