Psoriasis is a chronic disease that has negative effects on quality of life. Understanding the illness perception of psoriasis is important for effective management of the disease and improving quality of life. The aim of this study was to determine the relationship between illness perception and quality of life in psoriasis patients. This cross-sectional study was performed with 306 patients who applied to a psoriasis outpatient clinic of a university hospital in Istanbul, Turkey. Data were collected using a sociodemographic characteristics and disease information form, the Dermatology Life Quality Index (DLQI), the Revised Illness Perception Questionnaire (IPQ-R) and the Psoriasis Area Severity Index (PASI) score. Data were analyzed using descriptive statistics, Kruskal-Wallis test and Mann-Whitney U test, Spearman correlation analysis, and multiple regression analysis. A positive relationship was found between scores on the DLQI and scores on the IPQ-R subscales of Illness identity, Consequences, Emotional representations, Time (cyclic), Personal attributions, External attributions, and Chance. A negative correlation was determined between DLQI scores and scores on the IPQ-R subscales of Treatment control and Illness coherence. Furthermore, there was a positive correlation between the PASI score and the DLQI scores and scores on the IPQ-R subscales of Consequences and Emotional representation. Multiple regression analysis showed that illness identity, PASI scores, treatment control, illness coherence, consequences, and personal attributions were significantly associated with quality of life (R2 = 0.365, p < 0.01). The quality of life of the psoriasis patients who associated their symptoms with the disease, who had a high PASI score, thought that they were adversely affected by the disease, and who saw personal attributions as the cause of the disease was negatively affected. The quality of life of patients who thought that their disease could be kept under control and who understood their disease was positively affected.