Prime Minister Narendra Modi pulled off his first diplomatic coup even before taking office.
Pakistan Prime Minister Nawaz Sharif, Afghanistan President Hamid Karzai and Sri Lankan President Mahinda Rajapaksa were among some 4,000 guests who watched Modi and his new ministers take the oath of office and secrecy - a historic first for any prime ministerial inauguration.
The invitations to South Asian leaders showed Modi's determination to be a big player on the global stage after years of international isolation over the 2002 riots in Gujarat, the state he ruled till now.
After the ceremony, Sharif, who had called it a "great moment and great opportunity", was the first to shake hands with the new Prime Minister.
All South Asian leaders posed with the Prime Minister and President Pranab Mukherjee for an unprecedented photograph on the steps of the presidential palace.