In 2020, between 6% and 11% of women were recorded to be living with HIV/AIDS, against 3% to 6% of men in sub-Saharan Africa. The use of condom is a suitable mean of helping them to prevent the pandemic. The researcher adopted a cross sectional design and quantitative approach to conduct the study. This study involved 376 female sex workers living in Kigali city calculated by Yamane’s sample size formula. The snowball technique was used to reach the sex workers on prostitution sites or in their respective homes across the city of Kigali. The findings on the condom use within female sex workers in Kigali City revealed that 68.9% have been using consistently the condom in the previous 30 days while 31.1% do not use it constantly. 77.4% used the condom during their last sex while 22.6% did not use it. Multivariate analysis showed that sex workers being married was 3.74 times more likely associated with consistent condom use with AOR 3.74 95% CI (1.81-7.75), p<=0.01. Also, being new in the profession of sex working with a working experience of less than one year was four times more likely than having an experience of more than 1 year associated to consistent condom use, Adjusted OR 4.28 95% CI (2.10-8.73), p<=0.01. As recommendation, the government should put in place a program helping to sensitize the female sex workers to constantly use the condom as it was found that 31.1% do not use it despite its benefits in preventing HIV, STIs and unwanted pregnancies and in partnership with NGOs, the government should seek the effective manner of making the condom more affordable because 35.4% of sex workers have no financial means to buy the condom when they need it.