This book introduces the main ideas and fundamental methods of iso-differential calculus for iso-functions of several variables. Introduced are the iso-functions of the first, second, third, fourth and fifth kind, and iso-partial derivatives of the first, second, third, fourth, fifth, sixth and seventh kind. In this book, the main conceptions for multiple, line and surface iso-integrals for iso-functions of several variables are given. The book is provided with examples and exercises making it suitable for an introductory one- or two-semester undergraduate course on some of the major aspects of iso-differential calculus. Alternatively, it may be used for beginning graduate level courses and as a reference work. With exercises at the end of each chapter and its straightforward writing style, the book addresses readers who have no prior knowledge on this subject but have a basic background in graduate mathematics courses, such as theory of functions and differential calculus.