This book is an outcome of the lectures given for the courses taught in the subject Nuclear Physics in college level by the author over the years. This book is written in a simple, lucid and comprehensive style.The first part of the book is Nuclear Physics comprising chapters on basic nuclear structure, nuclear models, nuclear reactions and elementary particles. The second part deals with the environmental impact assessment of radiation in which the author stressed the environmental effects of radiation and nuclear pollution together with current environmental issues which are the burning challenges of the present day scenario. The model questions at the end of each chapter will help the students to have better insight and understanding of the subject. Many available standard books on the subject have been freely consulted for the preparation of this manuscript. I sincerely acknowledge my indebtedness to the authors and publishers whose books I have referred. The author is grateful to her student P.Usha Rajalakshmi, for her out-and-out service. The book is highly useful to college and university teachers, students, and all those concerned.