Non-surgical periodontal therapy (NSPT) represents the gold standard in the treatment of periodontitis, but deep periodontal pockets and complex anatomies may reduce its efficacy. Therefore, in order to enhance NSPT outcomes and reduce the need for surgical intervention, several adjunctive therapies have been proposed. Propolis, a natural substance with antimicrobial, anti-inflammatory, and healing properties, has shown promising results in controlling supragingival biofilm. This narrative review aims to assess the clinical efficacy of propolis as an adjunct to NSPT. A comprehensive search on scientific databases was conducted for randomised clinical trials (RCTs) comparing NSPT with and without propolis, or with other adjuncts or placebos. Probing depth (PD) was the primary outcome. Seven RCTs met the inclusion criteria, using different propolis formulations and application protocols. Statistically significant improvements in clinical outcomes were recorded in all analysed studies compared with NSPT alone or placebo, while benefits were less substantial compared with laser therapy and conflicting when compared with chlorhexidine. Thus propolis may be considered a promising adjunctive agent to NSPT, with the potential to improve clinical outcomes of NSPT. Nonetheless, further long-term clinical trials with larger sample size are needed to validate its clinical efficacy and to determine its adverse effects.