This study assessed the effects of Waltermart Supermarket on small retail businesses in Candelaria, Quezon, Philippines. Using the adapted questionnaire from Cantuba (2015), retailers assessed the effects of Waltermart on their sales and revenue, product movement, and customer attraction and retention using the 5-scale Likert style. The adapted questionnaire from Lee (2008) was also used to assess the strategic response of the retailers to maintain sustainable operation using marketing practices, merchandising practices, customer service practices, and business operation practices using 5-scale Likert style. A total of sixty registered retailers were used as the sample. Findings revealed that retailers are moderately affected by the presence of Waltermart with ‘customer attraction and retention’ ranked the highest, and ‘sales and revenue’ as the lowest. In terms of strategic practices used by retailers to maintain sustainable operation in the presence of Waltermart, findings revealed that ‘business operation practices’ ranked the highest, and ‘merchandising practices’ as the lowest. For this, retailers need to continue an effective business operation and enhance the quality, competitiveness, and availability of the product through good inventory quality control management. As the study offers an assessment of the effects of Waltermart on retailers, the results suggest an in-depth analysis of the impact of supermarkets on the retailer’s performance through financial ratios.