- Daniel Day-Lewis as Gerard Patrick "Gerry" Conlon
- Pete Postlethwaite as Patrick "Giuseppe" Conlon
- Emma Thompson as Gareth Peirce
- John Lynch as Paul Hill
- Corin Redgrave as Inspector Robert Dixon
- Beatie Edney as Carole Richardson
- John Benfield as Chief PO Barker
- Paterson Joseph as Benbay
- Marie Jones as Sarah Conlon
- Gerard McSorley as Detective Pavis
- Frank Harper as Ronnie Smalls
- Mark Sheppard as Patrick Joseph "Paddy" Armstrong
- Don Baker as Joe McAndrew
- Tom Wilkinson as an Appeal Prosecutor
- Anthony Brophy as Danny
Model, now actress, Saffron Burrows made her feature film debut in the film, as Gerry Conlon's free love-interest at a commune/squat in London at the time of the bombings.