OBJECTIVE: To determine the effect of aspiration and non-aspiration of syringe prior to intramuscular administration of influenza vaccine in pain perception of children 9 to 15 years of age consulting at the Out Patient Department of a Tertiary Government Hospital. DESIGN: Randomized controlled clinical Trial SETTING: Out Patient Department of a Tertiary Government Hospital PARTICIPANTS: One-hundred twenty children 9 to 15 years old consulting at the Out Patient Department. METHODOLOGY: Subjects were randomized into two groups and were given influenza vaccine with and without aspiration prior to intramuscular injection. OUTCOME MEASURES: Primary outcome measure is the degree of pain experienced by the subject using the Numeric Rating Scale. RESULTS: A total of one hundred twenty children were randomized to either Group A or Group B. IBMSPSS version 21 was used as statistical software. Differences in mean heart rate at baseline and after the intervention within group is significantly different (p value < 0.01). Mean heart rate in between group at baseline and after administration of influenza vaccine is not significantly different ( p value >0.05). The difference in mean oxygen saturation at baseline and after immunization within group is significantly different. Mean oxygen saturation between group pre and post immunization is not statistically different (p value 0.309). Analysis showed there is a significant difference in mean pain scores between Group A and Group B ( p value 0.046) CONCLUSION This study showed a statistically significant lower pain score for Group A (without aspiration) than Group B (with aspiration). The physiological pain responses, used as outcome measures in this study did not have significant differences between two groups. The result of this study will unleash in health care professionals the burden on whether or not to aspirate before intramuscular administration of vaccine.