Objectives The study aimed to determine the effect of oxymetazoline nasal spray on the patency of the fistula created after dacryocystorhinostomy, specifically: to compare the success of fistula formation with oxymetazoline versus placebo, and to compare the incidence of post-operative congestion, pain and bleeding with oxymetazoline versus placebo. Results The study was a single-center, randomized controlled, triple-masked study involving the patients of the Plastic-Lacrimal service of a national university hospital. Block randomization was done. Dacryocystorhinostomy was performed by a single-masked surgeon. The intervention group used oxymetazoline. The placebo group used sodium chloride. The data were collected by another masked investigator. The study showed no significant difference in terms of congestion, pain and epistaxis between the two groups at day 2 post-operation. The patency, presence of silicone tube, granuloma formation, and presence of bleeding on both day 2 and day 16 post-operation had no difference between the two groups. This study doesn’t support the use of oxymetazoline nasal spray after DCR, since it does not decrease the symptoms of congestion, pain and epistaxis after DCR. Aside from being an additional expense for patients, it also does not affect fistula formation and success rate of the surgery. Trial registration Australian New Zealand Clinical Trial Registry: ACTRN12619001394134, Date registered 10/11/2019, Retrospectively Registered.