Objective <p>To assess the impact of injectable platelet-rich fibrin (i-PRF) as an adjunct to scaling and root planing (SRP) in patients with periodontitis.</p> Materials and methods <p>Twenty-four patients, with two pairs of contralateral teeth (probing depth [PD] ≥ 5&#xa0;mm), were enrolled. The tooth pairs were randomly assigned to either the control group (SRP, <i>n</i> = 149 sites) or the experimental group (SRP + i-PRF, <i>n</i> = 135 sites). The clinical parameters PD, gingival recession (GR), clinical attachment level (CAL), plaque index (PI), and full mouth bleeding on probing (fBOP) were evaluated at baseline and 45 and 90 days. Radiographic analysis measured the distance from the cementoenamel junction to the alveolar bone crest (CEJ-BC) at baseline and 90 days.</p> Results <p>Both groups showed significant reductions in PD, CAL, fBOP, and PI from baseline to 45 days (<i>p</i> &lt; 0.001), without significant differences between the groups (<i>p</i> &gt; 0.05). The test group exhibited increased GR at 45 days (<i>p</i> &lt; 0.05). CEJ-BC decreased in both groups at 90 days with no significant intergroup difference (<i>p</i> &gt; 0.05). At 90 days, no significant intra- or intergroup differences were observed in any of the clinical parameters (<i>p</i> &gt; 0.05).</p> Conclusion <p>SRP alone or combined with i-PRF resulted in comparable clinical and radiographic improvements in patients with periodontitis. Adjunctive i-PRF did not offer significant additional benefits.</p> Clinical relevance <p>This study shows SRP alone and SRP + i-PRF yield satisfactory periodontal outcomes. Moreover, this study introduces the injection of i-PRF around the periodontal pocket, which, to the best of our knowledge, has not been extensively explored in the existing literature.</p> Trial registration <p><a href="https://ensaiosclinicos.gov.br/">https://ensaiosclinicos.gov.br/</a>: RBR-52h647m.</p>