Objectives <p>This study investigated the gingival crevicular fluid (GCF) levels of complement-C1q tumor necrosis factor related protein-1 (CTRP-1), tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) following non-surgical periodontal therapy (NSPT) in systemically healthy individuals with periodontal health (H), generalized gingivitis (G), and stage III grade B periodontitis (P). Moreover, this study aimed to investigate their diagnostic potential in distinguishing different periodontal diseases.</p> Materials and methods <p>73 systemically healthy non-smoking individuals were divided into H (<i>n</i> = 25), G (<i>n</i> = 23) and P (<i>n</i> = 25) groups. Clinical periodontal parameters were recorded, and GCF samples were collected at baseline in all groups, and 3rd month after NSPT in the G and P groups. GCF levels of CTRP-1, TNF-α, and IL-10 were analyzed using ELISA. The area under the curve (AUC) was assessed using the receiver operating characteristic curve analysis.</p> Results <p>CTRP-1 levels were significantly elevated in the G and P group compared to the H group (<i>p</i> &lt; 0.001), while there was no significant difference between the G and P groups (<i>p</i> = 0.095). TNF-α and IL-10 levels were significantly higher in the P group compared to the other groups (<i>p</i> &lt; 0.001). GCF CTRP-1 demonstrated an excellent diagnostic performance to discriminate periodontitis and gingivitis from periodontal health (AUC value of 0.998 and 0.974 with 100% and 91.3% sensitivity).</p> Conclusion <p>CTRP-1 could serve as a potential biomarker for periodontal diseases. CTRP-1 demonstrated excellent diagnostic performance in distinguishing stage III grade B periodontitis and gingivitis from periodontal health.</p> Clinical relevance <p>GCF CTRP-1 levels may serve as a valuable marker for diagnosing periodontal diseases.</p>