Psoriasis is a skin chronic inflammatory disease with a complex aetiology. It is characterised by the imbalance of environmental, genetic, and immunologic factors. Reactive oxygen species (ROS) could damage the cell components. The antioxidant system defends the body against ROS; a malfunction of the antioxidant system, together with an increased production of ROS, is involved in the pathogenesis of several diseases such as psoriasis. The purpose of this systematic review is to give an updated scenario about oxidative stress involvement in the psoriatic disease to identify useful biomarkers and to propose innovative therapies. A total of 28 studies were identified. Although several molecules were demonstrated being associated with psoriasis, only a little group resulted being eligible as disease biomarker [malonyldialdehyde (MDA), total oxidative stress, and oxidative stress index]. However, only MDA seems to be the best candidate for a clinical screening of psoriasis patients since it is intimately linked to Psoriasis Area Severity Index. Data suggest that current therapies with drugs, a healthy lifestyle, and the integration of a diet rich in antioxidants help to reduce the damage of oxidative stress caused by psoriasis, especially at the level of the skin. As much as we know, this is the first systematic review evaluating the oxidative stress role in psoriasis.