The objective of our study was to develop and test observational methods to evaluate COVID-19 preventive hygiene behaviors and physical distancing, and to evaluate the effectiveness of a government mandate on indoor fully covered mask wearing. An observational study was conducted of 4,736 individuals from April to October 2021 using 5-hour and rapid (10-minute) structured observations and spot checks to evaluate mask-wearing, handwashing, and physical-distancing behaviors, and the functionality of handwashing stations in 161 indoor public spaces across Bukavu, Democratic Republic of the Congo (DRC). Sixteen percent of individuals entering indoor public spaces were wearing a mask that fully covered their nose and mouth (fully covered mask wearing). Fully covered mask wearing was lowest inside schools (1%), universities (2%), religious establishments (22%), and health facility wards (28%). Overall physical distancing of more than 1-m inside indoor public spaces was 22%, and was lowest inside schools and religious establishments (7%). Thirty-nine percent of handwashing stations had water and a cleansing agent present. Ten percent of individuals washed their hands with a cleansing agent before entering an indoor space. Overall, fully covered mask wearing was similar for 5-hour and rapid structured observations (16% versus 15%). The odds of fully covered mask wearing was significantly greater with increased government enforcement of mask wearing in public spaces through fines (odds ratio, 2.72; 95% CI, 1.02-7.30). This study presents rigorous methods using structured observations to assess government mandates and programs on COVID-19 preventive hygiene behaviors in indoor public spaces in settings globally.