Background: The irrational use of antibiotics can cause an increase in antibiotic resistance that affects the number of mortality. Students undertaking profession program as co assistant dentists should have been equipped with knowledge on the rational use of antibiotics in the field of dentistry. Objective: This research aims to know the description of knowledge level of the first-year students of dentist profession study program on the use of antibiotics at RSGM UMY. Method: This is an observational descriptive research with cross sectional design. This research was conducted from May 15th 2019-June 29th 2019 at RSGM UMY. The subjects of the research were 121 people selected using total sampling technique. There were 118 participants who voluntarily participated in the research. The sample of the research was the first-year students of dentist profession study program at UMY. The data were obtained by distributing questionnaires consisting of 39 questions to the respondents. The obtained data were analyzed manually and displayed based on frequency distribution in the form of table. Result: The results show that the majority of the respondents have a low knowledge level on the use of antibiotics (74.7%). Based on five components on antibiotics use, nearly all respondents have a low knowledge level on the definition and classification (62.8 %), antibiotics dosage (67%), indication of antibiotics (77.2%), adverse effect of antibiotics (73%), and antibiotics resistance (48.3%). Conclusion: The majority of the first-year students of dentist profession study program has a low knowledge category on the use of antibiotics.