Llandaff RFC was formed in 1876 by Cambridge graduate Illtyd Thomas, and these links are reflected in the team still playing in Cambridge blue. It is believed that Llandaff were one of nine teams that were represented at the Tenby Hotel in 1880, in an early attempt to found the Welsh Rugby Union.
Playing against other South Wales club sides, they gained early success winning the South Wales Challenge Cup during the 1891/92 season. Unusual for a Welsh rugby team, Llandaff have played their rugby on the same pitch, Bishop's Field, since their inception, though like all clubs in Wales the team ceased playing during the First World War. The team reformed after the war but lost their WRU status, and could not play in official competitions. It wasn't until 1948 that Llandaff reapplied and were successful in regaining membership of the WRU.