Peter Wittingham's last-minute strike finally ended Leyton Orient's brave resistance at Ninian Park to send Cardiff to the Carling Cup third round.
Peter Wittingham celebrates his winner with Stephen McPhail
Wittingham's powerful shot squeezed in at the near post from a corner which resulted from one of many fine saves by visiting goalkeeper Stuart Nelson.
He denied Jimmy-Floyd Hasselbaink on numerous occasions, and fellow debutant Robbie Fowler twice hit the crossbar.
Orient's Sean Thornton was sent off for two yellow cards on 68 minutes.
Cardiff: Turnbull, Gunter, Purse (Blake 45), Johnson, Capaldi, Parry, Rae, McPhail, Whittingham, Hasselbaink, Fowler (MacLean 90).Subs Not Used: Oakes, Ledley, Ramsey.
Goals: Whittingham 90.
Leyton Orient: Nelson, Terry, Thelwell, Mkandawire, Palmer, Daniels, Thornton, Demetriou, Melligan (Chambers 70), Gray, Echanomi (Boyd 61).
Subs Not Used: Corden, Morris, Oji.
Sent Off: Thornton (69).
Ref: Mike Russell (Hertfordshire).