The 2023–24 LEN Euro Cup knockout stage details the matches played to decide the champion of the tournament.
The knockout phase involves 16 teams: the eight teams which qualified as winners and runners-ups of each of the four groups in the group stage, and the eight third and fourth placed teams from the Champions League group stage.
| Group | width=210 | Winners | width=210 | Runners-up |
|---|---|---|---|---|
| A |  CN Barcelona |  EN Tourcoing | ||
| B |  RN Savona |  A-Híd Vasas Plaket | ||
| C | Primorje Erste Bank Rijeka | BVSC-Zugló | ||
| D | Panionios GSS | CC Ortigia | ||
| Group | width=210 | Winners | width=210 | Runners-up |
|---|---|---|---|---|
| A | Astralpool Sabadell |  Steaua București | ||
| B | Jug AO Dubrovnik |  Dinamo Tbilisi | ||
| C |  Crvena zvezda |  Jadran Herceg Novi | ||
| D | Spandau 04 | NC Vouliagmeni | ||
The draw took place in Barcelona on 15 December 2023. The teams were split into two draws, one containing the four teams who finished fourth in the Champions League group stage, who would be pitted up against a Euro Cup group winner. The other half of the draw would see the third place teams from the Champions League group stage be drawn against a runner up of the Euro Cup group stage.[1] [2]
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Jug AO Dubrovnik won 21–19 on aggregate----Crvena zvezda won 23–22 on aggregate----Spandau 04 won 22–20 on aggregate----Astralpool Sabadell won 33–23 on aggregate----Steaua București won 31–30 on aggregate----Primorje Erste Bank Rijeka won 28–22 on aggregate----RN Savona won 28–23 on aggregate----NC Vouliagmeni won 27–19 on aggregate
The draw took place in Barcelona on 26 March 2024.[3] [4] There was no seeding.
Spandau 04 won 23–20 on aggregate----Astralpool Sabadell won 13–11 on aggregate----Jug AO Dubrovnik won 29–19 on aggregate----Primorje Erste Bank Rijeka won 24–23 on aggregate