This study aimed to evaluate whether ergothioneine (ESH) accumulated in catfish muscle affected to fillet quality during frozen storage. The fish after fed by feed supplemented 0 to 15% concentrated extract (CE) from Flammulina velutipes for 30 days were filleted and stored at −18 ± 0.2°C for 90 days. The results show that with 10% CE, the highest accumulation of ESH in fish muscle was 21.02 mg/Kg. During preservation, ESH decreased gradually with DPPH. Peroxide and FFA were the lowest value at 1.09 meq/Kg and 0.35% on day 90, respectively. L* achieved lower while a* and b* values were quite stable during the first 60 days. The a* dropped slightly, but the b* and ∆E increased slowest from days 60 to 90. The muscle hardness was more stable during storage. Therefore, high accumulation of ESH in catfish muscle could prevent lipid oxidation, improving color stability, and limit soft structure during frozen storage.