The use of face masks is one of the preventive measures that Mozambique adopted in order to limit the spread of COVID-19. A study carried out from May 25 to June 6, 2020 found that although many wore masks, incorrect use was observed in 27.5% of the population observed. This data collection aimed to measure the degree of mask use compliance during a more protracted, higher second wave of transmission. A cross-sectional study was conducted in the City of Maputo from 19 to 28 October 2020 through direct observation of mask use of all individuals present in markets, supermarkets and bus terminals. The data were collected using mobile phones with the Open Data Kit Collect (ODK) data collection program. Sociodemographic characteristics, mask use, and type of mask used were documented. Factors associated with incorrect mask use were evaluated considering sex, age, observation period and location. A total of 49,404 individuals were observed, of whom 24,977(50.6%) were male, 46,484 (94.1%) were adults and 17,549 (35.5%) were observed in the markets. An observed 41,786 (84.6%) wore a mask, of whom 33,851 (81.0%) used it correctly. Not covering the mouth and nose was common; observed in 4,649 (58.5%) of those using incorrectly. Of different types of masks, fabric masks were most often used incorrectly 7,225 (21.4%). The factors associated with incorrect mask use were female gender (OR = 1.2 [1.1-1.3], p <0.001), observation in peri-urban versus urban areas (OR = 1.9 [1.8-2.1], p <0.001) and observation during the afternoon (OR = 1.5 [1.5-1.6], p <0. 001). A high proportion of observed individuals wore a mask in the context of prevention of COVID-19, however some non-use and incorrect use persists. Intensified public awareness of the correct use of the mask is recommended, especially in peri-urban areas and at the end of the day.