Singh and Gilani shook hands as they greeted each other during the photo-op for the top world leaders attending the summit in the South Korean capital.
Singh was later seen having a longish chat with Chinese President Hu Jintao, who is set to visit India for the BRICS (Brazil, Russia, India, China, South Africa) summit in New Delhi this week.
Monday night, the Prime Minister and his Pakistani counterpart Gilani had a "meet and greet" encounter prior to a dinner hosted for dignitaries attending the summit here. "Prime Minister said hello to Mr Gilani," Indian sources had said.
Singh and US President Barack Obama also exchanged pleasantries and hugged each other when they came face-to-face at the summit on Monday.
Obama told Singh, "Nice to see you here Mr Prime Minister." The last Singh-Obama meeting had taken place on November 17, 2011 on the sidelines of the Association of Southeast Asian Nations (ASEAN) summit in Bali, Indonesia.