The present disclosure relates to system and method of authenticating online payment transactions. The method includes receiving a payment transaction request from a mobile device 110. Upon receiving the payment transaction request, a digital payment system 120 transmits a request for user’s biometric data for performing biometric authentication. Upon receiving the user’s biometric data from the mobile device 110, the digital payment system 120 compares the received biometric data with the user’s biometric data stored in a memory. If the biometric data matches, the digital payment system 120 approves the transaction and a notification is sent to the mobile device. The proposed method may help visually impaired users to authenticate payment transactions using the biometric means. Further, the proposed method also helps to reduce fraudulent transactions