Background: Nasal douching is commonly performed after endoscopic sinus surgery (ESS). There is a lack of studies comparing the clinical effect of various douching solutions after ESS. This study investigated the clinical effects of normal saline, lactated Ringer's, and hypertonic saline nasal douching solutions after ESS. Methods: Adult patients (41.8 ± 12.9 years) undergoing bilateral ESS for chronic rhinosinusitis at a single tertiary referral center were blindly randomized to one of the three study solutions and reviewed on postoperative weeks 1, 3, and 6. The 20-item Sino-Nasal Outcome Test (SNOT-20) scores, visual analog scale (VAS) symptom scores, digital video capture of the sinus cavities, and mucociliary clearance (MCC) times were performed at each visit. The mucosa appearances were scored by a second investigator, blinded to the douching solution. Results: Seventy-four patients were recruited. All groups showed an improvement with treatment in SNOT-20 scores and VAS scores, as well as endoscopic evaluation of mucosa appearance over time. There was no improvement of MCC during the treatment period. Irrigation with lactated Ringer's solution resulted in better symptom scores in SNOT-20 (p < 0.05) and VAS (p < 0.05), compared with irrigation with normal saline or hypertonic saline solutions. Patients receiving hypertonic saline solutions had less polypoidal mucosa at week 6. Conclusion: Douching with lactated Ringer's solution after ESS results in better improvement in sinonasal symptoms, compared with normal saline or hypertonic saline solutions.