Background: Periostin (POSTN), a matricellular protein released by fibroblasts, is an important regulator of bone development and connective tissue integrity in both healthy and diseased conditions. The goal of the current study was to measure the levels of POSTN in gingival crevicular fluid (GCF) in patients with aggressive and chronic periodontitis and compare them to healthy controls. Materials and Methods: A total of 90 people were recruited and divided into three groups: the healthy group, the two forms of periodontitis (chronic and aggressive), each with 30 participants. The GCF fluid samples were taken using a microcapillary pipette. With the aid of the enzyme-linked immunosorbent test, the POSTN levels were calculated. Results: The mean levels of total POSTN in GCF fluid (in pg/μl) were 182.41, 79.87, and 49.28 for the healthy, CP, aggressive periodontitis groups, respectively. There was a statistically significant difference between the groups with P < 0.05. Furthermore, there were statistically significant differences when compared among the groups with P < 0.05. When all three groups were examined together, there were negative correlations between GCF POSTN levels and clinical parameters. Conclusion: It was concluded that the levels of POSTN in GCF could be contemplated as a dependable marker in periodontal disease diagnosis and its activity.