This study examined perceived benefits and challenges of Mobile Phone Banking usage in the National Microfinance Bank (NMB) Dodoma, Tanzania. A cross-sectional design was used in which questionnaire was administered to 85 MPB customers and management team. Purposive and convenience followed by systematic sampling techniques were used to select respondents. NMB reports were reviewed in order to extract secondary data. The findings reveal a significant difference (p < 0.01) in transaction costs between MPB and ATM/traditional banking. Findings reveal that MPB has resulted into several perceived benefits to NMB customers including 24 hours availability, ease of use, high security, reduced queues, cheap, multiple services and transferability. Accordingly, network failure, theft of fund transferred, delay of fund delivery and reconciliation are challenges facing MPB usage. The study recommends to the NMB management that more promotional effort is required in order to attract new customers who are not subscribed to MPB. Also, Tanzania Communications Regulatory Authority (TCRA) needs to improve the stability of networks and enact laws against theft cases via MPB.