Orange pomace was extracted through SFE with CO2 added of different cosolvents. The results showed that global extraction yield increased, whereas antioxidant activity (both DPPH and ORAC assays) decreased at higher pressures. The TPC of the extracts varied between 18.0–21.8 mg GAE/g extract, with higher values at the highest pressure (35 MPa). No correlation between TPC and DPPH radical scavenging activity was observed. Literature suggests that antioxidant activity of citrus extracts is related to the content of ascorbic acid or its synergy with TPC. SFE had lower global yields and achieved about half the TPC obtained by Soxhlet extraction. Nevertheless, SFE required 78% less time and 10 times less ethanol than Soxhlet, so it is more economical in terms of time and energy consumption.The fermentation process of the orange pomace using the fungus P. variotii promoted the release phenolic compounds and thus increased the functional activity of antioxidant compounds for both SFE and low pressure solvent extraction. When the orange pomace was biotransformed, the TPC increased more than twice in SFE with CO2+ 6% ethanol–water(9:1 v/v) when compared with the non-fermented pomace. When different cosolvents were compared in SFE, the most polar cosolvent (mixture ethanol–water) improved the extraction of phenolic compounds and notably enhanced the functional activity of antioxidants. Although other extraction methods, such as pressurized liquid extraction, should be evaluated isolatedly or in sequential extraction processes in order to improve the phenolic recovery, SFE has shown potential to obtain valuable products from industrial by-products as orange pomace. The biotransformation process showed to be advantageous for the achievement of higher yields of phenolic compounds, besides enhancing the antioxidant capacity of the extracts due to hydrolysis of polyphenols into simple compounds with greater degree of hydroxylation.