The Indian banking sector can take advantage of the proliferation of smartphones as well as the government’s encouragement of cashless transactions to accelerate the use of mobile and online banking. The purpose of this study is to understand the initial acceptance of mobile banking by existing online banking users. Few studies have focused on online banking users’ behavioural intention to use similar services (such as mobile banking) in India. To this end, a theoretical model was developed using the technology acceptance model, which was extended to cover the adoption factors that influence users of online banking to use mobile banking. These adoption factors comprise perceived ease of use, perceived security, mobile self-efficacy, social influence and customer support. The dependent variable is customers’ behavioural intention to use mobile banking. A partial least squares structural equation modelling analysis was used to test the theoretical model with sample data from 420 online banking customers of various public, private, foreign and co-operative banks in India. The study found that the adoption factors had a significant impact on customers’ behavioural intention to use mobile banking. The findings of this study provide insight into digital banking channels, contribute to existing research on digital banking adoption and will educate banks and financial institutions on the adoption of mobile banking in India.