Extraction with pressurized carbon dioxide was applied to recover polyunsaturated fatty acids (PUFA) from striped weakfish (Cynoscion striatus) wastes. Extraction yield was evaluated at temperatures from 30 to 60 °C and pressures from 20 to 30 MPa. Temperature and pressure of 30 °C and 20 MPa were selected to evaluate process kinetics. A scale-up was performed by keeping the ratio constant between solid mass and solvent flow rate. Mathematical models were applied to the extraction curves, and the broken and intact cell model provided good fits, being applied to multiple curves simultaneously. Manufacturing cost of the extraction was estimated, and an optimal extraction time was observed by the end of the convective period. Finally, the extracts were analyzed by gas chromatography, and over 20% of the oil was composed by PUFA, whose concentration increased with extraction time. Therefore, this work shows that pressurized CO2 extraction can obtain valuable compounds from fish residues.