The fish-scaler tool is a multi-purpose fishing tool only available on some 91mm models. The ridged bottom edge of the tool is the fish scale remover. The tip is a U-shaped fish hook disgorger used to safely remove a hook from a fish's mouth. The tip is magnetized on some versions, empirical evidence suggests that those models were manufactured prior to 1985.

The fish-scaler was introduced in 1952 and originally had smooth sides. However, in 1975 a ruler was introduced to the tool (initially with inch graduations). Later versions have a metric scale on one side and an imperial scale on the other.

A novel usage for the fish-scaler is for Halloween pumpkin carving; the wide serrations are apparently ideal and because the tool is safe for younger carvers it might even be the best suited tool for the job ever! The shallow serrations can also be useful on soft materials, like styrofoam, that could clog up a sharper saw.

The forked tip can also be used as an impromptu cocktail fork, or key for paper towel dispensers or other insecure locks. The fish-scaler can also be used as a non-sharp prodding tool, if needed, as most other tools on a Swiss Army Knife are sharp.