| # | Book Title | Author | |
|---|---|---|---|
| 1 | The Fourth Floor Twins and the Fish Snitch Mystery | Adler, David A. | |
| 2 | Fourth Floor Twins and the Fortune Cookie Chase, The | Adler, David A. | |
| 3 | Fourth Floor Twins and the Disappearing Parrot Trick, The | Adler, David A. | |
| 4 | Fourth Floor Twins and the Silver Ghost Express, The | Adler, David A. | |
| 5 | Fourth Floor Twins and the Skyscraper Parade, The | Adler, David A. | |
| 6 | Fourth Floor Twins and the Sand Castle Contest, The | Adler, David A. |