Tricon's categories basically followed those of the previous year's Loncon II, but dropped the short-lived Best SF Book Publisher and added a one-time Best All-Time Series category. This was the last year for the Best Short Fiction Hugo, starting in 1967 it was split into Best Short Story and Best Novelette.
For the first time, Tricon permitted each voter to nominate three works in each category — previously voters were limited to a single nomination in each category.
Tricon did not release standings after first place.
- 1966 Best Novel Hugo: Dune by Frank Herbert
- 1966 Best Short Fiction Hugo: "'Repent, Harlequin!' Said the Ticktockman" by Harlan Ellison
- 1966 Best Dramatic Presentation Hugo: Insufficient nominations — not on ballot.
- 1966 Best Professional Magazine Hugo: If ed. by Frederik Pohl
- 1966 Best Professional Artist Hugo: Frank Frazetta
- 1966 Best Fanzine Hugo: ERB-dom ed. by Camille Cazedessus, Jr.
- 1966 Best All-Time Series Hugo: Foundation series by Isaac Asimov