Handwashing with soap is the most effective defense against contagious diseases but studies show that children do not routinely wash their hands using methods that healthcare agencies, such as the World Health Organization, have determined best practice. The purpose of this study was to evaluate the feasibility of a gamification-based handwashing intervention aimed at improving handwashing quality of kindergarten aged children. This cluster randomized controlled trial was conducted in three kindergartens in Southern Finland. Two experimental groups received intervention and one group acted as control. Study sample consisted of children aged 3–6 years old who were willing to participate in the study. Intervention consisted of tablets that were installed above handwashing stations at the kindergartens. Tablets guided correct handwashing steps to the children in real time and rewarded them with animal cartoon at the end of the handwashing event. The correct handwashing steps included wetting both hands, applying soap, scrubbing thoroughly, rinsing, and finally drying both hands. Primary outcome variable was determined as total score from correct handwashing steps performed. Structured observation was used as data collection method in three different time points and total of n=279 handwashing events were observed. Statistical analysis of the data was done using Kruskal-Wallis’ test and Chi-square test in SPSS version 27. In baseline phase there was no statistically significant difference between the experimental groups and control group in the handwashing quality of the children (p=0,063). In intervention phase handwashing quality of the children in the experimental group was statistically significantly better than in the control group (p<0,001). In intervention phase more children in experimental groups used soap in handwashing than in control group (p<0,001). The present study demonstrates that the gamification-based handwashing intervention may help to improve the handwashing quality and applying of soap of kindergarten aged children. Intervention is feasible to improve handwashing of kindergarten aged children, but it seems that its effects are not sustainable in long term.