This study was designed to assess knowledge, attitude and practices of adverse drug reaction reporting among healthcare professionals in Hiwot Fana Specialized University Hospital (HFSUH). Hospital based descriptive cross sectional study was conducted on healthcare professionals of HFSUH. Based on purposive sampling technique, all eligible healthcare professionals (nurses, physicians and pharmacists) were involved in the study. A pretested self-administered questionnaire was used to collect data. Data were coded, entered and analyzed using SPSS version 16. The test of association of selected categorical variables were done using cross tabulation and Pearson Chi-square test. Our study indicated that about 297 participants provided their response to the distributed questionnaires which makes the response rate 91.4%. Of the total healthcare professionals involved in the study, 99 (33.6%) of them were able to understand the difference between adverse drug reaction (ADR) and side effects, of which pharmacists were significantly reported (95.24%, P<0.05). About 175(59.3%) of the respondents engaged in the study were reportedly knew the national ADR reporting system in Ethiopia. On the other hand, 181(61.36%) of the participants were recognized the presence of ADR reporting form while 114 (38.64%) of the respondents had no any information about its presence in the country. The study revealed that a gap in knowledge, awareness and practice of healthcare professionals on ADR reporting. Therefore, specific strategies should be designed in order to improve awareness, knowledge and practice of healthcare professionals to tackle issue related to under-reporting of ADR.