This paper describes an attempt to identify the relationships between the using of a mobile device and an online shopper's trust in use of electronic payment systems in order to see how the adoption of a mobile device can contributes positively to increase shoppers' trust in their used of electronic payment systems. Therefore, this trust will increase shopper's intention to purchase online. It also investigated whether the availability of a security-enabled mobile device, modified to provide added security for an online shopper's payment details, would influence their intention to use online shopping. The study was based on a well-established theoretical model for the adoption of a Mobile Device Payment System (MDPS) with the Technology Acceptance Model (TAM). Structural Equation Model (SEM) techniques were used to analyze the data. Results from a survey showed that the adoption of mobile devices had strongest direct effect on increase an online shopper's trust in the electronic payment systems.