"His sentence is based on credible, specific evidence proving his involvement in espionage and terrorist activities in Pakistan, resulting in the loss of scores of precious lives of Pakistanis," Foreign Office (FO) spokesman Nafees Zakaria said.
He said Mr Jadhav was found guilty after a "fair trial according to the law of the land".
"Inflammatory statements emanating from India are against international norms and will only result in escalation of tension, serving no constructive purpose. India's reaction should be seen in the backdrop of exposure of its state involvement in perpetrating subversive and terrorist activities in Pakistan," he said.
Mr Zakaria said the reaction from India especially withholding the release of Pakistani prisoners who had completed their sentences was "disappointing".
He said India was displaying "complete disregard" for the UN Charter and International Covenant and Conventions and challenging the international community.
Pakistan claims its security forces had arrested Mr Jadhav from the restive Balochistan province on March 3 last year after he reportedly entered from Iran. It also claimed that he was "a serving officer in the Indian Navy".
The Pakistan Army had also released a "confessional video" of Mr Jadhav after his arrest.
However, India denied Pakistan's contention and maintained that Mr Jadhav was kidnapped by the Pakistan authorities.
India had acknowledged that Mr Jadhav had served with the navy but denied that he has any connection with the government.