Purpose: Patients might refuse the offer of local anaesthesia (LA) administration prior to dental treatment. This study investigates subjective discomfort perception during non-surgical mechanical periodontal therapy delivered with or without LA. Materials and Methods: Sixty patients with mild to moderate chronic periodontitis and prior periodontal debridement experience were randomly enrolled in nonsurgical therapy of a quadrant with or without LA administration. Patients were free to comply or not with the allocated LA arrangement. Visual analogue scales (VAS) of discomfort perception at various stages of the treatment as well as overall satisfaction were recorded. Demographic, psychosocial and periodontal parameters were recorded. Results: Thirty-one patients undergoing nonsurgical periodontal therapy not receiving (LA-) and 29 participants receiving LA (LA+) were studied. Compared to LA- patients, LA+ individuals perceived less discomfort during treatment and reported less dental anxiety (p 0.05). Lower overall treatment satisfaction was associated with prior unpleasant periodontal experience (p = 0.047). Overall, debridement discomfort was associated with not receiving LA, noncompliance with the pain control regimen allocated, longer treatment duration, greater gingival inflammation and a higher percentage sites with probing pocket depths ≥ 5 mm (p 0.05). Conclusion: Clinicians should be aware that patients who refuse LA can experience higher dental anxiety and therefore may require various pain control strategies for comfort during nonsurgical periodontal therapy, which, if not employed, can lead to less periodontal treatment satisfaction. Keywords: dental fear, periodontitis, psychosocial aspects, root planing