Hercule Poirot – retired detective who investigates the central murder.
Roger Ackroyd – wealthy businessman and widower who is distressed by the recent death of the woman he wants to marry, Mrs Ferrars.
Mrs Cecil Ackroyd – Mr Ackroyd's widowed sister-in-law. She lives with her brother-in-law the last two years, having no other means and is woman of fast-changing opinions.
Flora Ackroyd – Mr Ackroyd's niece and Mrs Cecil Ackroyd's daughter. She is engaged first to Ralph at her uncle's request, then to Major Blunt, on her own preference.