Objective: This study aimed to compare Th17-related cytokines named IL-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, IFN-γ, sCD40L and TNF-α in peri-implant fluid (PIF) from mucositis sites in patients having either peri-implantitis, periodontitis or without interproximal alveolar bone loss. Material and methods: Thirty-three patients diagnosed with peri-implant mucositis were divided into three groups: individuals with peri-implant mucositis but without any signs of interproximal alveolar bone loss (group 1, n = 10), individuals with peri-implantitis (group 2, n = 14) and individuals with periodontitis (group 3, n = 9). Probing depth (PD), clinical attachment level (CAL), visible plaque index and bleeding on probing were measured. PIF was collected from mucositis sites in patients from the three groups and from peri-implantitis (group 2) and periodontitis sites (group 3). Cytokines were measured by a bead-based multiplex assay. Results: Probing depth was significantly lower in group 1 when compared to both groups 2 and 3 (P < 0.001 and P = 0.01, respectively). There was no significant difference in cytokine levels in mucositis sites among the three groups. In group 2, IL-21 level was significantly higher in mucositis compared to peri-implantitis sites (P = 0.04). Conclusion: The expression of Th17-related cytokines in PIF from mucositis sites seems to be similar regardless the presence or not of alveolar bone loss around implants or teeth.