This book constitutes refereed proceedings of the Third International Conference on Emerging Technology Trends in Electronics, Communication and Networking, ET2ECN 2020, held in Surat, India, in February 2020.The 17 full papers and 6 short papers presented were thorougly reviewed and selected from 70 submissions. The volume covers a wide range of topics including electronic devices, VLSI design and fabrication, photo electronics, systems and applications, integrated optics, embedded systems, wireless communication, optical communication, free space optics, signal processing, image/ audio/ video processing, wireless sensor networks, next generation networks, network security, and many others.