Abstract Objective To assess the effect of sialendoscopy of the major salivary glands on salivary flow and xerostomia in patients with Sjögren’s syndrome (SS). Methods Forty-five patients with SS were randomly assigned to a control group (no irrigation, control, n = 15), to irrigation of the major salivary glands with saline (saline, n = 15) or to irrigation with saline followed by corticosteroid application (triamcinolone acetonide in saline, saline/TA, n = 15). Unstimulated whole saliva flow (UWSF), chewing-stimulated whole saliva flow (SWSF), citric acid-stimulated parotid flow, Clinical Oral Dryness Score (CODS), Xerostomia Inventory (XI) and EULAR SS Patient Reported Index (ESSPRI) scores were obtained 1 week before (T0), and 1, 8, 16, 24, 36, 48 and 60 weeks after sialendoscopy. Data were analysed using linear mixed models. Results Irrespective of the irrigation protocol used, sialendoscopy resulted in an increased salivary flow during follow-up up to 60 weeks. Significant between-group differences in the longitudinal course of outcomes were found for UWSF, SWSF, XI and ESSPRI scores (P = 0.028, P = 0.001, P = 0.03, P = 0.021, respectively). UWSF at 60 weeks was higher compared with T0 in the saline group (median: 0.14 vs median: 0.10, P = 0.02) and in the saline/TA group (median: 0.20, vs 0.13, P = 0.035). In the saline/TA group SWSF at 48 weeks was higher compared with T0 (median: 0.74 vs 0.38, P = 0.004). Increase in unstimulated salivary flow was also reflected in improved CODS, XI and ESSPRI scores compared with baseline. Conclusion Irrigation of the major salivary glands in patients with SS increases salivary flow and reduces xerostomia.