 Gregory PeckCapt. Horatio Hornblower R.N | Capt. Horatio Hornblower R.N |
 Virginia MayoLady Barbara Wellesley | Lady Barbara Wellesley |
 Robert BeattyLt. William Bush | Lt. William Bush |
 Moultrie KelsallLt. Crystal | Lt. Crystal |
 Terence Morgan2nd Lt. Gerard | 2nd Lt. Gerard |
 James KenneyMidshipman Longley | Midshipman Longley |
 James Robertson JusticeSeaman Quist | Seaman Quist |
 Denis O'DeaRAdm. Sir Rodney Leighton | RAdm. Sir Rodney Leighton |
 Richard HearnePolwheal (Hornblower's Batman) | Polwheal (Hornblower's Batman) |
| MMichael DolanSurgeon Gundarson | Surgeon Gundarson |
 Stanley BakerMr. Harrison (Bosun) | Mr. Harrison (Bosun) |
 Alan TilvernHernandez | Hernandez |
 Alec MangoEl Supremo (Don Julian Alvarado) | El Supremo (Don Julian Alvarado) |
 Christopher LeeSpanish Captain | Spanish Captain |
| JJohn WittyCapt. Entenza | Capt. Entenza |
 Michael GoodliffeCol. Caillard - POW Escort | Col. Caillard - POW Escort |
 Eugene DeckersFrench Commandant | French Commandant |
 Ingeborg von KusserowHebe (Lady Barbara's Maid) | Hebe (Lady Barbara's Maid) |
 Amy VenessMrs. McPhee (Hornblower's Housekeeper) | Mrs. McPhee (Hornblower's Housekeeper) |
 Kynaston ReevesAdm. Lord Hood | Adm. Lord Hood |
 Ronald AdamAdm. McCartney | Adm. McCartney |
| CChris AdcockCrewman (uncredited) | Crewman (uncredited) |
| BBasil BartlettCapt. Elliott (uncredited) | Capt. Elliott (uncredited) |
| AAndré BelhommeFrench Guard (uncredited) | French Guard (uncredited) |
| DDavid BirksCrewman (uncredited) | Crewman (uncredited) |
| RRobert Cawdron"Witch of Endor" French Mate (uncredited) | "Witch of Endor" French Mate (uncredited) |
 Diane CilentoMaria Hornblower (voice) (uncredited) | Maria Hornblower (voice) (uncredited) |
| HHoward Connell"Lydia" Seaman (uncredited) | "Lydia" Seaman (uncredited) |
 Alexander DavionSpanish Officer (uncredited) | Spanish Officer (uncredited) |
| SSteve DonahueCrewman (uncredited) | Crewman (uncredited) |
