Reference intervals of intraocular pressure (IOP) are poorly described in piscine species as the factors that may influence it. Rebound tonometry was used to measure IOP in 28 adult brook trout (Salvelinus fontinalis) anesthetized in a buffered solution of 60 mg/L tricaine methanesulfonate (n = 16) or restrained with electronarcosis (n = 12) at 16 mA. There was no significant effect of the eye side, sex, fish origin, and body weight, but IOP values were significantly higher with electronarcosis (mean ± SD: 16.4 ± 5.0 mm Hg) than with immersion anesthesia (10.8 ± 3.3 mm Hg; P = 0.0017). The same restraint method should be used for comparison with previously published IOP values or when evaluating individual variations over time.