Background: Nasogastric tube insertion is a common but distressing procedure in young children. We aimed to compare the efficacy of topical local anaesthetic and vasoconstrictor nasal spray with placebo for distress related to nasogastric tube insertion. Methods: We did a prospective, randomised, controlled, double-blind, superiority trial in a single tertiary paediatric emergency department in Australia. Eligible participants were children aged 6 months to 5 years who were planned to have a nasogastric tube inserted as part of their emergency department treatment. Patients were assigned using computer-generated block randomisation to receive lidocaine and phenylephrine nasal spray (10 mg lidocaine and 1 mg phenylephrine for children weighing 6–12 kg; 20 mg lidocaine and 2 mg phenylephrine for children weighing >12 kg), or 0·9% sodium chloride placebo nasal spray, before nasogastric insertion. Guardians, observers, and proceduralists were all masked to the intervention. The primary outcome was procedure-related distress, measured using the Face, Legs, Activity, Cry, and Consolability (FLACC)scale during the final attempt at nasogastric tube insertion. All patients were included in the primary analysis (intention-to-treat). FLACC scores were compared using the Wilcoxon rank-sum test, and categorical outcomes were compared using χ2 or Fisher's exact tests as appropriate. This study is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12614000092695. Findings: Between July 30, 2014, and Aug 17, 2017, 107 children in a convenience sample were randomly assigned to receive lidocaine and phenylephrine nasal spray (n=54)or placebo (n=53). Seven children did not receive study medication (six no longer required nasogastric tube insertion and one withdrew consent). 50 children received each intervention; all were included in the analysis. There was no difference in median FLACC score at time of nasogastric tube insertion (9 [IQR 7–10]for lidocaine and phenylephrine vs 9 [IQR 8–10]for placebo; median difference between groups −1, 95% CI −2·7 to 0·7, p=0·21). Adverse effects of the spray or nasogastric tube insertion (most commonly vomiting and gagging)occurred in 14 (28%)of those who received lidocaine and phenylephrine and 21 (42%)of those who received placebo. Interpretation: Lidocaine and phenylephrine nasal spray does not reduce procedure-related distress associated with nasogastric tube insertion in young children compared with placebo. Further research addressing distress associated with nasogastric tube insertion in young children is needed. Funding: Monash Health Senior Medical Staff Association, Australasian College for Emergency Medicine, Emergency Medicine Research Foundation.