(1) Background: Rheumatoid arthritis (RA) is a chronic autoimmune disease associated with an increased incidence of metabolic syndrome (MetS). The aim of this study was to determine if there is an association between MetS and parameters of RA activity, as well as between metabolic parameters and indices of RA activity. (2) Methods: This study involved 65 patients with RA. MetS was diagnosed according to the 2009 IDF/AHA/NHLBI criteria. The comparative analysis was conducted between RA patients with MetS (RA (MetS (+)) and without MetS (RA (MetS (−)). The activity of RA was assessed using clinical, laboratory, and ultrasound (US) parameters. (3) Results: Compared with RA MetS (−) patients, RA MetS (+) patients were characterized by higher disease activity, according to Disease Activity Score (DAS28), Simplified Disease Activity Index (SDAI), and Clinical Disease Activity Index (CDAI). RA MetS (+) patients had significantly higher tender and swollen joint counts, and values of erythrocyte sedimentation rate, C-reactive protein, and US parameters (grey-scale (GSUS), power Doppler (PDUS)). Significant correlations were found between metabolic parameters (waist circumference, cholesterol and glucose concentrations) and indices of RA activity. (4) Conclusion: The results of this study show that, in patients with RA, the presence of MetS is associated with higher disease activity, based on several clinical, laboratory, and US parameters.