Polyphosphates are legally permitted additives that are widely used to aid in processing for improving eating quality of many foods, particularly meat and fish products. Usage of polyphosphate to fish before freezing often helps to reduce the amount of thaw drip that is the liquid releasing when frozen fish is thawed. Applying a large amount of polyphosphate in fish processing is occurring in a lot of frozen fish companies which can become a negative factor to the development of exported products. The objective of this study was to determine the effects of various phosphate blends and treatment conditions (method, temperature, and time of tumbling) on the quality and safety of frozen Tra fillets in Mekong Delta, Vietnam. Tra fillets were dipped in brine solutions consisting of 0.5% NaCl and 1.1% phosphate for 15 minutes. Three kinds of phosphate solutions were applied for this experiment: (i) sodium tripolyphosphate (STPP), (ii) mixture of STPP + sodium polyphosphate, and (iii) STPP + sodium polyphosphate + sodium diphosphate.  The ratio of Tra fillets and solution was 2:1. In addition, the optimal temperature for phosphate treatment was observed. Fillets were evaluated for drip loss, tumbling yield, color, pH, tenderness, water holding capacity, and sensory properties. It was found that STPP gave a significant lower drip loss (P < 0.05) and higher pH value than other treatments. All phosphate treatments significantly decreased (P < 0.05) the tenderness, especially STPP blends significantly (P < 0.05) improved the lightness of the product. When temperature conditions in a range of 6÷12ºC were applied for phosphate treatment, there was not significant (P < 0.05) change in the yield and the quality of Tra fillets. Accordingly, the treatment of Tra fillet with solution of STPP at 9÷12ºC was chosen.