Fintech services and E-commerce are the terms used to describe the use of technology in financial services and commerce transactions. Fintech is the main driver for financial inclusion, focusing on providing all financial services at a low cost with a larger scale and broader reach. The E-commerce platforms provide an amazing solution for more complex problems, provide very high efficiency in supply chain management. They make the cash cycle more fast and efficient as well as can easily control business processes. E-commerce will be a reduction in costs, as well as boost the marketing strategies, and thus can also increase the traffic on the businesses' E-commerce platforms. The compilation of the content of this monograph book provides the specific contents of behavioral assessments of using Fintech services and E-commerce. The quantitative models in the behavioral assessments of using Fintech services and E-commerce are introduced to find out the factors affecting the behavioral assessments of using Fintech services and E-commerce. The content of the book, "Behavioral Assessments of Using Fintech Services and E-Commerce" associates the Fintech services and E-commerce with the quantitative models, not going into proving the testing tools of econometrics but focusing on application tools in analyzing the results of quantitative models. Each quantitative model used in the behavioral assessments of using Fintech services and E-commerce has important implications in many angles. The quantitative models will provide theoretical and empirical foundations that contribute positively to research and practical applications for many readers, students and postgraduate students.