Serhiy Melnyk was born on July 12, 1977, in Khmilnyk, Vinnytsia region.

He holds multiple degrees in higher education. In 1999, he graduated from Kharkiv Military University. In 2009, he obtained his second degree from the Yaroslav Mudryi National Law Academy. In 2019, he completed his studies at the National Academy of the National Guard of Ukraine. In 2022, he successfully completed a strategic-level senior management course at the National Defense University of Ukraine.

Melnyk has served in the Armed Forces of Ukraine since 1994. From 1999, he served in Air Defense Brigades and held senior positions at the Military Law Institute of the Yaroslav Mudryi National Law University. In April 2016, he was appointed Head of the Military Law Faculty at the same university. In November 2019, he became Head of the Military Law Institute.

Since the beginning of the full-scale invasion, he has been in charge of the defense of the city of Kharkiv.

Melnyk holds a Doctor of Law degree and is a Professor of Military Law. He is a recipient of the title "Honored Worker of Education of Ukraine" and winner of the State Prize of Ukraine in Education. He has also been awarded the Order of Bohdan Khmelnytsky, III degree.

On October 11, 2024, the Cabinet of Ministers of Ukraine appointed Serhii Melnyk as Deputy Minister of Defense of Ukraine.