Xi, who met Modi in a never-seen-before setting at Wuhan last year, said he attached great importance to Sino-India ties and take them to new heights.
"On the occasion of the National Democratic Alliance winning the 17th Lok Sabha elections on India under your (Modi) leadership, I would like to extend my heartfelt congratulations," Xi said in a letter to Modi.
The Chinese President is expected to meet Modi in India later this year in a two-day Wuhan-like format where they had several rounds of talks including informal chats.
In his congratulatory message sent even before the official election results, Xi noted that under the leadership of the two leaders, Sino-Indian ties "have shown strong momentum of development".
"As important neighbours to each other, China and India are the two largest developing countries and emerging economies in the world. In recent years, China-Indian relations have shown strong momentum of development under the joint efforts of both sides.
"China and India maintain good coordination and cooperation on major issues such as promoting multi-polarization, economic globalization as well as upholding multilateralism," the Chinese President said in an oblique reference to his country's on-going trade spat with the US.
"I attach great importance to the development of China-India relations and would like to work with you to guide the development, directions of the bilateral relations, enhance mutual political trust, expand pragmatic cooperation and promote the closer developmental partnership between the two countries to a new height.
"With my best wishes for your good health and every success," Xi added.
( With inputs from IANS )