Background: Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the joints, especially of the hands. The evaluation of handgrip strength (HS) and pinch strength can be useful to detect reduction in hand function in RA patients. The aim of the study was to compare HS and pinch strength between RA patients (RA Group-RAG) and a non-RA control group (CG) and to relate HS and pinch strength to functional capacity, duration and disease activity in the RAG. Methods: A cross-sectional case control study. The RAG was assessed for disease activity by the Disease Activity Score (DAS-28); for functional capacity by the Health Assessment Questionnaire (HAQ), the Cochin Hand Functional Scale (CHFS) questionnaire, and the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire; and for HS and pinch strength (2-point tip-to-tip, lateral or key, and 3-point) using Jamar® and pinch gauge dynamometers, respectively. Associations were analyzed by Pearson and Spearman tests, and groups were compared by the independent samples t test, with a significance level of P < 0.05. Results: The convenience sample included 121 rheumatoid patients and a control group matched by age, sex, and body mass index. The RAG showed lower strength values compared with the CG in all measurements (P < 0.01, 95% CI) and these values were associated with worse performance in the functional questionnaires and greater disease activity and duration. There was a strong correlation among the functional assessment instruments. Conclusions: The decrease in grip and pinch strength, easily measured by portable dynamometers, is a strong indicator of functional disability in RA patients.