Cardiff recorded their first win over Leinster since January 2022, climbing to third in the URC table. The hosts led 3-0 at halftime through a Callum Sheedy penalty before extending their advantage when Aled Davies scored a counter-try in the 54th minute.
Leinster responded with a converted try by Luke McGrath in the 68th minute but Cardiff held on despite being reduced to 14 men after Jacob Beetham's yellow card.