High hydrostatic pressure (HHP) applied to wine in flexible plastic bottles has been studied as an enological practice for red wine aging, due to the oxidative reactions that can be promoted by this technology. To evaluate the effect of HHP on wine phenolic composition, a red wine treated with HHP was compared with different conventional wine aging processes, such as the use of wood and microoxygenation. The wine was pressurized at 500 MPa for 5 min at 20 °C and the same wine was also stored in oak barrels and treated with oak chips with or without microoxygenation. For comparison of the HHP effect, all wines were stored in polyethylene bottles. After 5 months, the monomeric anthocyanins, phenolic acids, and flavonols content of pressurized wines were lower in comparison with the other wine treatments. Nevertheless, pressurized wines showed a similar degree of tannin polymerization, pyranoanthocyanins content, and percentage of prodelphinidins in relation to the wine treated with microoxygenation and oak chips. HHP, possible by promoting a higher diffusion of oxygen into the wine, has the potential to be a novel oenological practice, producing red wines with a polymeric phenolic composition similar to those treated with wood aging processes.