Aim Aim of this study was to investigate the influence of an anti‐inflammatory diet on different parameters in patients with gingivitis. Materials and Methods Thirty patients were randomly allocated to an experimental and a control group stratified by their plaque values. The experimental group had to change to a diet low in processed carbohydrates and animal proteins, and rich in omega‐3 fatty acids, vitamin C, vitamin D, antioxidants, plant nitrates and fibres for 4 weeks. The control group did not change their diet. Both groups suspended interdental cleaning. Periodontal parameters were assessed by a blinded dentist. Serological and subgingival plaque samples were taken at baseline and end. Results While there were no differences regarding the plaque values, the experimental group showed a significant reduction in gingival bleeding (GI Baseline: 1.04 ± 0.21, GI End: 0.61 ± 0.29, p < 0.05), a significant increase in Vitamin D values and a significant weight loss. There were no inter‐group differences regarding the inflammatory serological parameters, the serological omega fatty acids, nor the subgingival microbiome composition. Conclusion The evaluated diet could significantly reduce gingivitis in a clinically relevant range, while serological inflammatory parameters and the subgingival microbiome seem to be unaffected in this study duration. (German Clinical Trials Register; DRKS00009888).