Queueing at the shopping malls gives hassle to the customers especially during peak time such as festive seasons. Pre-purchase has been acknowledged as a solution to the problem. With the advancement of technology especially smartphone and mobile apps, pre-purchase can be done anywhere and it can avoid customers from long queueing at the cashier counter. Therefore, this paper reports the usability of a mobile app called ShopCart among customers at shopping malls. For this study, a service-based mobile app has been developed by applying Near Field Communication (NFC) technology. In short, ShopCart enables customers to scan the groceries they wish to buy using NFC and the items will then be recorded in the ShopCart. Payment will finally be made online and the groceries will be sent to home. Usability evaluation using questionnaire method has been conducted involving 87 respondents. Results shown ShopCart has scored more than 75 for all three usability criteria which are effectiveness, efficiency and satisfaction. © 2018 IEEE.