Evaluation of the relationship between cognitive distortions and depression and anxiety levels is important for the diagnosis, treatment and care of depression and anxiety. The aim of this study is to systematically examine the relationship between cognitive distortions and depression and anxiety levels. In this systematic review, Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) criteria were used. Scopus and Elsevier/ClinicalKey/ScienceDirect and PubMed, Cochrane, Web of Science electronic bibliographic databases were searched between 15 February -5 April 2019 by using the following keywords "cognitive distortion, cognitive error, cognitive biases, depression, anxiety, cognitive distortion, cognitive error, cognitive bias, depression, anxiety". 14 studies were included in the assessment. The participants of six of these studies are healthy; eight of these consists of the case group which have participants diagnosed with depression or anxiety and consist the control group which have healthy participants. Four of these studies were carried out with cross-sectional design, two with Randomized Control, one with Prospective Descriptive Case Series design, five with Prospective Case-Control, two with Prospective Comparative Case Series design. The results of the studies; shows that there is a positive relationship between cognitive distortion level and anxiety or depression levels of individuals who are healthy or have been diagnosed with depression and / or anxiety. Studies show that cognitive distortion level; They found that they were positively associated with depressive symptoms, anxiety symptoms, adult separation anxiety, social anxiety, negative self-expression, decreased socio-emotional functioning, hopelessness, rumination, aggression, dysphoria and suicide attempt. In addition, in two intervention studies aimed at reducing cognitive distortions, it was determined that with cognitive distortions decreased and symptoms of depression and anxiety decreased