Introduction: The oral hygiene practices are very low among primary school students and the incidence of dental problems is high. Objective: To assess the skill in tooth brushing technique and to evaluate the effectiveness of demonstration on skill in tooth brushing technique. Methods: One group pretest posttest design was used in the study. Forty primary school students were selected using non probability convenience sampling technique from Govt. lower primary School Kadayiruppu, Ernakulam district, Kerala. The data was tabulated and analyzed using differential statistics like frequency (f), percentage (%), mean, standard deviation (SD) and inferential statistics paired “t” test. Results: The mean post test skill score (17.5) was greater than the mean pre test skill score (9.5). There was significant difference between pretest skill scores and posttest skill scores (t = 21.62, p = 0.001). Conclusion: The study has shown demonstration on skill in tooth brushing technique among primary school students was effective in terms of improving their skill level. There is an immense need of creating skill among primary school students regarding brushing technique to keep their teeth strong and healthy and nurses are in the best position to reach and teach the students.