Using mobile phones for financial transactions has been on a sharp increase globally and in Tanzania in particular. The introduction of mobile money interoperability allows customers to undertake money transfers across different telecom mobile money accounts and bank accounts. This study aimed to find out factors that may influence the acceptance and successful use of mobile money services interoperability that are tailored to banking and unbanked users' intention by integrating three globally accepted theories; DeLone and McLean information system success model (D&M), The Technology Acceptance Model (TAM) and The Task-Technology Fit (TTF) Theory. The study hypotheses were empirically tested using data from 447 mobile money users from both telecom and banks. Data were analysed using the correlation and regression technique. This study found that approximately 81.5% of the dependent variable, which is interoperability of mobile money services was accounted for by the regression analysis and therefore can strongly be explained very well by independent variables which are Perceived Ease of Use; price value; Network Availability; Security and Trust; Service quality; Task Characteristics. This study's findings provide valuable understandings for formulating effective strategies concerning financial inclusion to mobile money service providers, governments, and other stakeholders and expand the existing customer base to mobile money service providers. Moreover, this study's results will provide the basis for further refinement of technology acceptance and success models in the emerging mobile money service domain. I. INTRODUCTIONToday, mobile phones can be used as a means of communication and the means of financial inclusion in most low-income countries. 65% of adults in the world's poorest economies still lack access to even the most basic transaction account that would allow them to send and receive payments more safely and efficiently (Pazarbasioglu et al., 2020). The mobile phone has made mobile money services possible and now reaches millions of unbanked low-income populations in developing countries, especially in rural areas (GSMA, 2019; Demirguc-Kant et al., 2018). According to UNCTAD (2019), mobile money has improved financial inclusion, making it easier, real-time insight at a lower cost, cheaper and safer to transfer money, and paying for goods and services. By the end of 2019, 5.2 billion people subscribed to mobile services, accounting for 67% of the global population, and forecasted that in 2023 more than $1 trillion will be transacted via mobile platforms annually, with over $2.8 billion a day (GSMA, 2020). Evidence shows that there are over 1.04 billion registered mobile money accounts worldwide, of which 469 million are from Sub-Saharan Africa. There are 229 live mobile money deployments in 95 countries transacting US dollars 40.8 billion processing over US dollars 1.9 billion per day globally (GSMA, 2019). Tanzania has experienced explosive growth in the use of mobile money since the