| Cardiff vs | Merthyr | ||||
| Matches | 30 | ||||
| Won | 23 | ||||
| Lost | 7 | ||||
| Drawn | 0 | ||||
| Points For | 733 | ||||
| Points Against | 446 | ||||
| Date | Home | Away | Venue | ||
| 11/01/1877 | Cardiff | 0 | 0 | Merthyr | Cardiff Arms Park, Cardiff |
| 19/10/1878 | Merthyr | 0 | 0 | Cardiff | Plymouth Ground, Pentrebach |
| 23/10/1880 | Cardiff | 0 | 0 | Merthyr | Cardiff Arms Park, Cardiff |
| 23/09/1907 | Merthyr | 3 | 13 | Cardiff | Unknown |
| 30/03/1933 | Merthyr | 8 | 22 | Cardiff | Unknown |
| 01/03/1934 | Merthyr | 3 | 20 | Cardiff | Unknown |
| 07/03/1935 | Merthyr | 3 | 11 | Cardiff | Unknown |
| 20/02/1936 | Merthyr | 6 | 11 | Cardiff | Unknown |
| 04/10/1937 | Merthyr | 6 | 19 | Cardiff | Unknown |
| 17/12/1994 | Cardiff | 63 | 8 | Merthyr | Cardiff Arms Park, Cardiff |
| 11/08/2004 | Merthyr | 10 | 29 | Cardiff | The Wern, Merthyr Tydfil |
| 30/08/2008 | Merthyr | 14 | 36 | Cardiff | The Wern, Merthyr Tydfil |
| 23/08/2014 | Merthyr | 11 | 26 | Cardiff | The Wern, Merthyr Tydfil |
| 10/09/2016 | Merthyr | 24 | 18 | Cardiff | The Wern, Merthyr Tydfil |
| 02/09/2017 | Cardiff | 24 | 17 | Merthyr | Cardiff Arms Park, Cardiff |
| 04/11/2017 | Merthyr | 27 | 23 | Cardiff | The Wern, Merthyr Tydfil |
| 27/01/2018 | Cardiff | 12 | 37 | Merthyr | Cardiff Arms Park, Cardiff |
| 09/02/2018 | Cardiff | 20 | 25 | Merthyr | Cardiff Arms Park, Cardiff |
| 01/09/2018 | Cardiff | 18 | 24 | Merthyr | Cardiff Arms Park, Cardiff |
| 14/12/2018 | Merthyr | 28 | 34 | Cardiff | The Wern, Merthyr Tydfil |
| 28/04/2019 | Cardiff | 25 | 19 | Merthyr | Principality Stadium, Cardiff |
| 14/12/2019 | Cardiff | 20 | 3 | Merthyr | Cardiff Arms Park, Cardiff |
| 16/10/2021 | Merthyr | 31 | 26 | Cardiff | The Wern, Merthyr Tydfil |
| 27/11/2021 | Cardiff | 29 | 45 | Merthyr | Cardiff Arms Park, Cardiff |
| 28/04/2022 | Cardiff | 31 | 12 | Merthyr | Cardiff Arms Park, Cardiff |
| 17/09/2022 | Cardiff | 50 | 15 | Merthyr | Cardiff Arms Park, Cardiff |
| 07/01/2023 | Merthyr | 16 | 22 | Cardiff | The Wern, Merthyr Tydfil |
| 06/05/2023 | Cardiff | 39 | 7 | Merthyr | Cardiff Arms Park, Cardiff |
| 16/12/2023 | Merthyr | 20 | 45 | Cardiff | The Wern, Merthyr Tydfil |
| 13/04/2023 | Cardiff | 47 | 24 | Merthyr | Cardiff Arms Park, Cardiff |