Literally, yantras means 'instruments' and in Hindu scriptures they are attributed to different Gods and Goddesses. They are used in the form of different metals articles and herbs. In Hindu Shastras yantras are held in high esteem and prescribed by astrologers and tantkriks to ward off evil effects of planets, souls etc. there are other uses such as Vashi karan, Uchattan, Sthamban, Vidveshan and Shantikaran in six rites besides the spiritual usages. Yantra is the medium through which the invincible force or energy acts on an individual. For that, the sanctity of the medium should be sustained and the person who wears it may also recite mantras to enhance the efficacy to the yantra. These are beneficial only to those who follow the prescribed rituals sincerely to get relief from the problems due to any dosha. The book deals with yantra pooja, design on yantras, the mantras being used for worshiping the yantra, energizing (praan prathishtha) the yantra and other usages of the yantras. This book is the first part of our work on tantra, mantra and yantra. The contents of this book are purely based on old Sanskrit classics. A detailed method of worshiping the yantras is given in the book which would be beneficial for the readers.