Background The COVID-19 pandemic is impacting the global community in many ways. Combating the COVID-19 pandemic requires a coordinated effort through engaging public and service providers in preventive measures. The government of Ethiopia had already announced prevention guidelines for the public. However, there is a scarcity of evidence-based data on the public knowledge, attitude, and practice (KAP) and response of the service providers regarding COVID-19. Objective This study aimed to assess the public KAP and service providers' preparedness towards the pandemic in Addis Ababa, Ethiopia. Methods A community-based cross-sectional study was conducted in Addis Ababa, Ethiopia, from late March to the first week of April 2020. Participants were conveniently sampled from 10 different city sites. Data collection was performed using a self-administered questionnaire and observational assessment using a checklist. All statistical analysis was performed using SPSS version Descriptive statistics, correlation coefficient and chi-square tests were performed. Result A total of 839 public participants and 420 service providers enrolled in the study. The mean age was 30.30 (range = 18-72) years. The majority of the respondents (58.6%) had moderate knowledge about COVID-19, whereas 37.2% had good knowledge. Moreover, 60.7% and 59.8% of the participants had a positive attitude towards preventive measures and good practice to mitigate the pandemic, respectively. There was a moderate positive correlation between knowledge and attitude, whereas the correlations between knowledge and practice and attitude and practice were weak. With regard to service providers' preparedness, 70% have made hand-washing facilities available. A large majority of the respondents (84.4%) were using government-owned media followed by social media (46.0%) as a main source of information. Conclusion The public in Addis Ababa had moderate knowledge, an optimistic attitude and descent practice. The information flow from government and social media seemed successful seeing the majority of the respondents identifying preventive measures, signs and symptoms and transmission route of SARS-CoV-2. Knowledge and attitude was not associated with practice, thus, additional innovative strategies for practice changes are needed. Two thirds of the service provider made available hand washing facilities which seems a first positive step. However, periodic evaluation of the public KAP and assessment of service providers' preparedness is mandatory to combat the pandemic effectively.