Various similarities have been observed between gingival crevicular fluid (GCF) and peri-implant sulcular fluid (PISF). This has resulted in research that has evaluated similar biological fluid markers that are similar to those present within the gingival sulcus. These biomarkers have high sensitivity and are a reliable biological tool when compared to clinical and/or radiographic examination and aid in diagnosis as well as monitoring the progression of periodontal disease surrounding teeth as well as the implants. The study aimed to compare the effectiveness of periostin in peri-implant sulcular and gingival crevicular fluids. This experimental prospective in vitro analysis was done following clearance by the institutional ethical committee. A total of 100 patients were selected. They were categorized into two groups: (I) Group A patients had peri-implant disease (n = 50), whereas (II) Group B patients had periodontitis (n = 50). Clinical loss of attachment score was noted in six sites around natural teeth and four sites around the implants. Presterilized filter paper strips were inserted within the sulcus/pocket till pressure was felt for 60 s. Periostin concentration levels in GCF and PISF samples were measured by the enzyme-linked immunosorbent assay technique. Statistical analysis of data collected was performed using Shapiro-Wilk statistical tool for normally distributed numerical data. Mean ± standard deviation concentration of periostin in gingival crevicular fluid from periodontitis cases was recorded as 20.15 ± 2.76 ng/30sn, whereas in PISF was 19.23 ± 1.89 ng/30sn. On statistical analysis, no statistically significant differences were seen after comparing the concentration of periostin in periodontitis as well as peri-implantitis groups (P > 0.05). The present study analyzed periostin levels in gingival crevicular fluid obtained from patients diagnosed with periodontitis and sulcular fluid obtained from the sulcus around implants. Early biological markers or indicators of inflammation should be studied to determine the prognosis of treatment apart from the clinical assessment for the patient's benefit.