Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by severe cognitive decline, for which current therapies are limited in efficacy and have significant adverse effects. In this context, natural compounds with neuroprotective potential are attracting increasing interest. Mansorina (MA), a coumarin derivative extracted from Mansoria gagei, is recognized for its antioxidant and anti-inflammatory properties. The aim of this study was to evaluate the effects of mansorina on cognitive function, using Danio rerio (zebra fish) as a preclinical model for AD. Amnesia was induced by exposing fish to okadaic acid (OKA, 10 nM) for 4 days. Animals were divided into six groups (n = 10/group): control (DMSO), OKA, galantamine (GAL, 1 mg/L), and OKA co-treated with MA at 1, 3, or 6 μg/L. MA was administered for 7 days, every 3 days, during water changes. Fish behavior was monitored using ANY-maze® v6.3 software (Stoelting Co., USA) and a Logitech HD Webcam C922 camera, for automatic analysis of locomotor and exploratory parameters in the Y-maze (spatial memory) and NOR (novel object recognition) tests. Statistical analysis was performed using ANOVA with Tukey’s post hoc test (GraphPad Prism 9, p < 0.05). OKA significantly impaired spatial memory and object recognition (p < 0.0001), effects reversed by GAL. MA at 3 and 6 μg/L improved cognitive performance (p < 0.001–0.00001) and increased exploration of the novel arm and object. MA also enhanced locomotor activity, suggesting a neuroactive effect.