Abstract: High-glucose environments induce cellular stress, particularly endoplasmic reticulum stress (ERS) and oxidative stress, in aquatic animals. Taurine, known for its cell-protective properties, has potential in mitigating such stress. This study investigated taurine's effects on ERS, oxidative stress, apoptosis, and glycogen accumulation in golden pompano (Trachinotus ovatus) muscle cells under high-glucose conditions. Cells were cultured with varying glucose concentrations and taurine supplementation. Techniques including Cell Counting Kit-8 (CCK-8) assay, Nile Red staining, periodic acid–Schiff (PAS) staining, and transmission electron microscopy (TEM) were used to assess cell viability, lipid deposition, glycogen accumulation, and ultrastructural changes, respectively. High glucose increased the ADP/ATP ratio, reactive oxygen species (ROS) levels, and reduced mitochondrial membrane potential (MMP), activating AMP-activated protein kinase (AMPK). This led to glycogen accumulation via increased glycogen synthase (gysm) expression and decreased glycogen phosphorylase (pygm) expression. Taurine supplementation restored glycogen balance, reduced glucose transporter 4 (GLUT4) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) protein levels, and alleviated ERS, as evidenced by reduced PKR-like ER kinase (perk) mRNA and glucose-regulated protein 78 (GRP78) protein expression. Also, taurine improved mitochondrial function, inhibiting apoptosis by reducing cytochrome C (CytC) release. In conclusion, taurine alleviated ERS, glycogen accumulation, apoptosis, and mitochondrial oxidative stress, providing new insights into taurine's mechanisms and supporting its potential use as a feed additive in aquaculture.