The two leaders discussed convergence of interests between India and China with Wen observing that "we are like drivers on the steering wheel driving in the right direction."
Commenting on the gesture, an Indian official observed that, "Wen is a man, who the Chinese themselves say, is responsible for giving a push to India-China relationship."
The lunch, hosted just before Singh wound up his three-day visit here, was also attended by Planning Commission Deputy Chairman Montek Singh Ahluwalia, National Security Adviser Shivshankar Menon and Foreign Secretary Sujatha Singh.
The Indian understanding is that Wen is pushing for India-China relationship in the Asian context and saw creation of opportunities between the two countries.
The gesture is rare as leaders in China generally go into obscurity after their retirement unlike Wen.
When asked about the lunch, Chinese Foreign Ministry spokesperson Hua Chunying said the two leaders met as they were friends for long.
"The reason is very simple. It is because Wen is an old friend of Prime Minister Singh. This kind of arrangement reflects the importance the Chinese side attaches to the visit by Prime Minister Singh," she said.