Purpose: To investigate whether genetic variations in cytokine genes involved in the pathogenesis of peri-implantitis are associated with the occurrence of peri-implantitis, an issue that remains controversial and may vary according to the population evaluated. Materials and Methods: A cross-sectional analytical study was carried out on 102 Caucasian Portuguese individuals who were divided into two groups: (1) 43 individuals with peri-implantitis and (2) 59 individuals with good peri-implant health. Samples from the buccal mucosa were obtained, and genetic analysis was performed using the real-time polymerase chain reaction (PCR) technique for IL-1A and IL-1B and PCR for IL-1RN. Results: The IL-1A-889 C/T polymorphism presented with a higher prevalence of the less common allele (T allele) in patients with peri-implantitis (27.9%) than in healthy patients (16.9%), but without statistical significance (P = .060). For the IL-1B+3954 C/T and IL-1RN (variable number of tandem repeats [VNTR]) polymorphisms, analysis revealed that the allele and genotype frequencies did not differ significantly between groups. There was a significant association between a history of periodontitis and peri-implantitis (P = .020). Conclusions: The evaluated genetic polymorphisms had no influence on the occurrence of peri-implantitis in the study population. Further research into genetic variations in different populations is needed to elucidate the role of genetic factors in the onset and progression of peri-implant disease.