Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disorder that mainly affects the diarthrodial joint. Morning stiffness and symmetric swelling of the wrists, PIPs and MCPs constitue the typical history for rheumatoid arthritis. Extra-articular manifestations in RA include constitutional symptoms, distinct organ manifestations and severe multiorgan disease. The presence of rheumatoid factor and the anti-cyclic citrullinated peptide antibody, which is more specific to RA, are helpful in RA diagnosis. Although conventional radiographs remain the initial imaging modality in patients with RA, other imaging modalities such as MRI or ultrasound have demonstrated increased sensitivity to detecting early erosive change. To the present day, there is no single test that confirms RA. Early diagnosis of RA is essential because there is substantial evidence that early therapeutic intervention with non-biologic/biologic disease-modifying antirheumatic drugs leads to a better outcome. Although the 1987 American College of Rheumatology (ACR) classification criteria for RA have been used as the gold standard in clinical studies, these criteria are misleading early in the disease course. The ACR/European League Against Rheumatism (EULAR) is scheduled to release the new classification criteria for RA soon. This review describes clinical manifestations of RA, diagnostic tools, as well as the classification criteria in the diagnosis of RA.