Introduction: Undernutrition among under-five children is a very common issue in Malaysia, especially among the Orang Asli population. Therefore, identifying the prevalence and factors associated with undernutrition will assist in tackling the issue of undernutrition and reducing the morbidity and mortality rate associated with it. Methods: A total of 47 conveniently selected Orang Asli children aged 6 to 59 months from Kampung Paya Bungor, Gambang, Kuantan, Pahang participated in this cross-sectional study. A face-to-face interview was carried out by using the validated Questionnaire for the Study of Malnutrition in Rural Malaysia 2009. The weight and height of the children were measured and plotted on the growth chart. All the data were analyzed using IBM SPSS Statistics Version 24.0. Descriptive statistics was used to describe the background characteristics of the respondents and univariate analyses were used to identify suitable factors to be included in multivariate analysis. Binary logistic regression was done to determine independent factors associated with undernutrition. Results: The overall prevalence of undernutrition was 55.3%. The prevalence of underweight, stunting and wasting was 34.0%, 34.0% and 14.9% respectively. This research also revealed that gender (p=0.042) and family size (p=0.024) was shown to have a statistically significant association with undernutrition. However, there were no significant associations between undernutrition with other factors. Conclusion: The prevalence of undernutrition among under-five Orang Asli children was a concern. It was found that the factors associated with undernutrition were female children and children from small families. Prompt interventions aimed at the Orang Asli community should be done to overcome these problems.