Background: Bronchial asthma (BA) is a chronic non-communicable disease affecting children and adults. Despite the availability of written guidelines for diagnosis and management, yet still knowledge and application were inadequate. The aim of this study was to assess asthma knowledge of primary health care centers (PHCCs) personnel in Dammam city, eastern Saudi Arabia. Materials and Methods: This was a cross-sectional study conducted in 22 PHCCs. The sample consisted of 194 personnel (50 physicians and 144 nurses). Data was collected through a self-administered questionnaire which contained 58 questions. Knowledge score about asthma was coded as good and poor. Descriptive statistics, paired t-test and logistic regression were used for statistical analysis. Results: The majority of PHCCs personnel (96.9%) had no postgraduate studies and 78.4% of them didn’t receive any training about BA. More than half (55.2%) of the PHCCs personnel showed good total knowledge score about BA. Also, 81.8% of the physicians and 52.7% of the nurses had good total knowledge level regarding the total aspects of BA in children. Physicians had statistically higher mean knowledge score than nurses regarding all components and total knowledge scores. Knowledge about role of exercise and prognosis was inadequate. Being a physician, female, younger, less years of work in PHCCs were statistically significant and associated with good knowledge level. Conclusions: There are still some deficiencies in knowledge about different aspects related to bronchial asthma. It is recommended that both physicians and nurses receive training about national asthma guidelines through continuing medical education.