Objective An increasing number of studies have demonstrated cognitive impairment in patients with rheumatoid arthritis (RA). The literature indicates many factors play an important role in this clinical problem, such as the severity of depressive symptoms and the treatment used. The aim of this study was to systematically review studies comparing cognitive functioning between healthy participants and RA patients and to determine both the severity and potential moderators of cognitive impairment. Methods For this purpose, 16 studies that fulfilled all selection criteria were carefully selected. Altogether, 921 patients with RA (812 women and 109 men) and 700 controls participated in these studies. Due to the inability to perform a network meta-analysis, it was decided to determine the effect sizes for studies which used the same measurement methods. Results The analysis demonstrated greater impairment of cognitive functioning in patients with RA than in healthy controls, with effect sizes ranging from small to large, depending on the assessment method used in the study. Conclusions The study pinpoints potential biases, lack of replication, and inconsistencies in reporting data as possible confounding factors and suggests further recommendations for assessment methods, research directions and clinical implications. Clinical trial registration Not applicable.