This book presents the core principles of heat and mass transfer in a clear and structured manner, making it ideal for engineering courses across various disciplines. Covering both fundamental and advanced concepts, it systematically explores conduction, convection, and radiation for heat transfer, as well as mass diffusion and convection for mass transfer. The first eleven chapters focus on heat transfer, addressing steady-state and transient conduction, forced and natural convection, phase change phenomena, heat exchanger design, and thermal radiation. The final chapter introduces mass transfer to maintain thematic continuity. Throughout the book, theoretical explanations are complemented by practical applications, numerical methods, and numerous solved and proposed problems-many drawn from real exam questions. With over 30 years of teaching experience, the first author brings deep expertise to the subject, ensuring a pedagogical approach that supports both learning and problem-solving skills.