G-protein beta 3 subunit (GNB3) C825T (rs5443) single nucleotide polymorphism (SNP) has been implicated as a risk factor for essential hypertension in the general population. The effects of this SNP may be more prominent in subjects with endothelial dysfunction (ED). Rheumatoid arthritis (RA) is associated with ED and has a high prevalence of hypertension. Thus far, this SNP has not been studied in RA patients. We genotyped 383 RA patients and 432 controls. GNB3 C825T was identified using real-time polymerase chain reaction (PCR) and melting curve analysis. There were no differences in the frequencies of the GNB3 C825T genotype and alleles between RA and controls. Within RA patients, prevalence of hypertension did not differ across genotypes. The TT versus CC+CT contrast yielded an adjusted odds ratio (OR) of 0.92 (95% CI: 0.49 to 1.76, p = 0.813), the contrast of TT+CT versus CC an adjusted OR of 2.17 (95% CI: 0.885 to 5.30, p = 0.091), whereas that of the T allele versus C allele an adjusted OR of 1.11 (95% CI: 0.76 to 1.61, p = 0.604). Systolic and diastolic blood pressure levels were not significantly different across the three genotypic groups. No significant interaction was observed between GNB3 825C/T polymorphism and serum endothelin levels. Data from the present study suggest that the T825 variant of the G protein beta 3 subunit gene is unlikely to constitute major susceptibility loci for essential hypertension in Caucasian RA patients. Further larger studies are required to confirm our findings and assess the interaction of rs5443 with environmental factors.