Dr. Castro has published in topics related to international finance, financial management, and monetary economics. He has also published several books on finance and economics. His most recent textbook (2019), co-authored with his daughter, Esther Castro, is the Principles of Quantitative Finance. Given his strong quantitative and data analytics background, Dr. Castro is looking to use this textbook to teach students and help businesses and banks with forecasting. He is currently working on other books related to Personal Financial Planning.

Most recently, Dr. Castro has been interested in researching how to alleviate poverty through financial education and microfinance. By studying the transmission of financial remittances which have become a major phenomenon in economics and international finance as a main source of income among poor people, the financial support through microfinance to establish small businesses, and getting financial education in which poor people can improve their standard of living. He was awarded SIFE's HSBC Financial Literacy Award for creating financial and economic opportunity in east Texas by helping the community develop personal financial management skills necessary to achieve financial independence.