Periodontal diseases are chronic inflammatory conditions affecting the supporting structures of teeth and represent one of the leading causes of tooth loss worldwide. Non-surgical periodontal therapy (NSPT), primarily consisting of scaling and root planing (SRP), remains the cornerstone of periodontal disease management. The primary objectives of NSPT are to eliminate microbial biofilm, reduce inflammation, arrest disease progression, and promote periodontal healing. Recent advances in instrumentation, adjunctive antimicrobial therapies, laser-assisted procedures, and host modulation therapies have further enhanced treatment outcomes. This review evaluates the clinical outcomes of non-surgical periodontal therapy by examining changes in periodontal parameters, microbiological profiles, patient-reported outcomes, and long-term disease control. Evidence suggests that NSPT significantly improves probing depth, clinical attachment levels, bleeding on probing, and periodontal inflammation while reducing pathogenic bacterial load. The study concludes that NSPT remains a highly effective first-line treatment modality and forms the foundation of comprehensive periodontal care.