| 1 | Mrs. | Ferrars | Has an affair with Roger. |
| | Ashley | Ferrars | Mrs. Ferrar's husband. |
| | Dr. James | Sheppard | Protagonist. Roger's close friend. |
| | Caroline | Sheppard | James's ingenious sister. |
| | Annie | | Sheppard's house parlourmaid. |
| 2 | | | King's Abbot - The village where James lived. |
| | | | Cranchester - A big town in King's Abbot. |
| | | | King's Paddock - An important house owned by Mrs. Ferrars. |
| | | | Fenly Park - An important house owned by Roger. |
| | Roger | Ackroyd | A successful manufacturer. The life and soul of King's Abbot. |
| | Mrs. | Ackroyd | Dead ex-wife of Roger. A dipsomaniac. |
| | Ralph | Paton | Roger's stepson. Mrs. Ackroyd's son. |
| | Miss | Russell | One of Roger's housekeepers. |
| | Cecil | Ackroyd | Roger's widowed sister-in-law. |
| 3 | Flora | Ackroyd | Ralph's step cousin. Engaged to Ralph. Roger's niece. |
| | Hercule | Poirot | Private detective. aka: Mr. Poirot. |
| | Miss | Gannett | Chief of King's Paddock newsmonger. |
| 4 | Parker | | Roger's butler. |
| | Geoffrey | Raymond | Roger's secretary. |
| | Hector | Blunt | Police major. Roger's friend. |
| | Mrs. | Bates | Calls in Sheppard's. |
| | Jones | | Inspector Davis's assistant. |
| 5 | Inspector | Davis | Police inspector in the Roger Ackroyd Murder Case. |
| | Colonel | Melrose | Chief constable. |
| 6 | Inspector | Raglan | Co-inspector of Inspector Davis. |
| 7 | Mr. | Hammond | Roger's family solicitor. Roger's lawyer. |
| | Elsie | Dale | Roger's maid. |
| | Ursula | Bourne | Roger's parlormaid. Ralph's secret wife. aka: Ursula Paton. |
| | Mrs. | Cooper | Roger's cook. |
| | Gladys | Jones | Roger's housemaid. |
| 10 | Richard | Folliot | Ursula's ex-boss. |
| | Mrs. | Bennett | Dr. Sheppard's patient. |
| | Dolly | Grace | Dr. Sheppard's patient. |
| | George | Evans | Dr. Sheppard's patient. Has ulcer. |
| 12 | Bruce | Macpherson | A Scotch gentleman. |
| | Colin | Macdonald | A Scotch gentleman. |
| | Clara | | Annie's friend. Miss Gannett's maid. |
| 14 | Colonel | Carter | Dr. Sheppard's guest at the little mahjong party. |
| 15 | Major | Elleby | Parker's former master. |
| | Charles | Kent | A stranger who visited Fenly Park the night Roger died. Barmaid. |
| 16 | SP | Hayes | Police superintendent. Poirot's former colleague. |
| | Inspector | Japp | Police inspector from Scotland. |
