Mobile banking (m-banking) allows consumers to conduct financial transactions without temporal and spatial constraints through Internet-enabled mobile devices such as smartphones. The adoption patterns are of particular research interest because m-banking penetration has been relatively low even though smartphones are the most dominant forms of mobile computing in the United States. Of these consumers with smartphones, Internet access, and a bank account; 68% used Internet, 33% used telephone-based banking, and only 21% engaged in some type of m-banking activities in 2011. The purpose of this correlational quantitative study was to explore the factors affecting m-banking adoption in the United States. The 7 constructs used to develop the web-based survey for this study were derived from the technology acceptance model (TAM) extended by the innovation diffusion theory (IDT). Data were collected by e-mail from a random sample of 398 people in the United States. The structured equation modeling (SEM) technique was used to assess correlations between the extended TAM constructs (independent variables) with m-banking adoption (dependent variable). The results indicated that, perceived compatibility, perceived credibility, and perceived costs were the significant predictors of m-banking adoption in the United States. The findings of this study provide marketers, smartphone manufacturers, and financial institutions the needed knowledge to help expand m-banking. This study contributes to social change because expanding m-banking is expanding opportunities to previously under-served populations who can afford cheap mobile phones to engage in financial activities. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]