The overall baseline (as received) moisture, protein and fat content of hybrid catfish (Ictalurus furcatus x Ictalurus punctatus) fillets were 77.8 +/- 1.38%, 16.7 +/- 0.50% and, 5.7 +/- 1.6%, respectively. Small fillets (111 +/- 19 g) had higher (P≤0.05) baseline moisture (78.6 +/- 0.87% vs 76.8 +/- 1.15%) and lower (P≤0.05) fat content (4.7 +/- 0.64% vs 6.8 +/- 1.72%) than large fillets (247 +/- 62 g), whereas protein content was similar (P>0.05) for both sizes. Retained water of the final fresh and frozen fillets was 1.2 +/- 2.03% and 3.1 +/- 1.02%, respectively, irrespective of fillet size. Psychrotrophic (PPC) and total coliform plate counts (TCC) of the baseline fillets were 4 log CFU/g and 1.6 log CFU/g, respectively and were not different between the process steps, except after injection which was higher (P>0.05) than baseline. Moisture-protein ratio and fat content were good (P≤0.05) predictors for retained water in catfish fillets during processing.