| Name | Character | Episodes |
|---|---|---|
| Sarah Selby | Aunt Gertrude Hardy | 35 |
| Russ Conway | Fenton Hardy | 35 |
| Tommy Kirk | Joe Hardy | 35 |
| Tim Considine | Frank Hardy | 35 |
| Carole Ann Campbell | Iola Morton | 35 |
| Arthur Shields | Boles | 20 |
| Donald MacDonald | Perry Robinson | 20 |
| Robert Foulk | Jackley the Plumber | 20 |
| Florenz Ames | Silas Applegate | 20 |
| Andy Clyde | Lacey | 15 |
| Hugh Sanders | Mr. Binks | 15 |