There are clinical difficulties to differentiate elderly-onset rheumatoid arthritis (EORA) patients from those with polymyalgia rheumatica (PMR), especially when dealing with EORA-like PMR-onset, seronegative EORA, and PMR with peripheral synovitis, which constitute the subgroups presenting the greatest difficulties. Serum samples were obtained from two groups of patients, one with EORA diagnosis and another with a PMR diagnosis. Anticyclic citrullinated peptide (anti-CCP) antibodies (enzyme-linked immunosorbent assay method) and rheumatoid factor (RF; latex technique) were determined. Of the 16 EORA patients, 9 presented anti-CCP antibodies, 4 of whom tested positive for RF. Of the 12 EORA patients who remained negative to RF, 5 were positive for anti-CCP antibodies. Eight of the EORA patients started with polymyalgic symptoms. Three of these patients showed positive titles of anti-CCP antibodies with negative RF. All PMR patients presented negative anti-CCP antibodies, except one with weak positive titles, and all were negative for RF. Of 15 patients with PMR, 7 presented oligoarticular synovitis at the onset. After a mean follow-up of 3 months, two patients developed RA. When evaluating them for RF and anti-CCP antibodies, one tested negative, while the other was positive for both antibodies. We observed a tendency to higher values of anti-CCP antibodies in patients with extraarticular manifestations, radiological damage, and disease-modifying antirheumatic drugs. When compared to the PMR group, EORA patients presented positive anticitrulline antibodies at the beginning of the disease in a statistically significant amount. One third of the seronegative EORA patients presented positive anti-CCP antibodies at the onset.