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. |