The study presented in this paper is focused on processing squid wastes by using sub-critical water extraction and hydrolysis to produce valuable substances. Using a small-scale batch reactor (9.0 cm(3)), squid entrails were treated with sub- and supercritical water without oxidants. Reaction conditions involved temperatures of 443-673 K, pressures 0.792-30.0 MPa, and reaction times 1-50 minutes. Fat and oil were extracted into sub-critical water very efficiently, and soluble proteins, organic acids, and amino acids were produced in the aqueous phase by a hydrolysis reaction. Even in the short reaction time of 5 min, more than 99% of solid were converted to those products in the temperature, which was higher than 550 K. Results showed a maximum total yield of sixteen amino acids of 0.1031 kg/kg dry entrails at 473 K (5 min), and a maximum total yield of seven organic acids of 0.055 kg/kg dry entrails at 553 K (40 min). Also the oil extracted with hexane included useful fatty acids. Our experimental results indicated that the sub-critical water treatment method is very efficient for converting waste squid entrails to valuable materials as resources for many other industries.