"As we devote ourselves to take India's development journey to newer heights, we seek your support, blessings and active participation," Modi said in his first message on the website.
"Together, we will script a glorious future for India. Let us together dream of a strong, developed and inclusive India that actively engages with the global community to strengthen the cause of world peace and development," the message said.
The website also uploaded a short profile of the new PM on www.pmindia.nic.in, describing him as "dynamic, dedicated and determined" leader who "arrives as a ray of hope in the lives of a billion Indians".
An option called "Wish the Prime Minister" takes a user to Modi's personal website.