India is among the 53 nations that make up the Commonwealth, which the British monarch described as "guardians of a precious flame".
"Not only are there tremendous rewards for this cooperation, but through dialogue we protect ourselves against the dangers that can so easily arise from a failure to talk or to see the other person's point of view," she said in her traditional broadcast message recorded at Buckingham Palace.
She said: "Indeed, it seems to me that now, in the second decade of the 21st century, what we share through being members of the Commonwealth is more important and worthy of protection than perhaps at any other time in the Commonwealth's existence.
The broadcast, which was themed around 'A Young Commonwealth' this year, was also be streamed at Westminster Abbey where the Queen joined 2,000 people, including senior royals and representatives from Commonwealth countries, for the annual Commonwealth Day service.
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"As a concept that is unique in human history, the Commonwealth can only flourish if its ideas and ideals continue to be young and fresh and relevant to all generations," she said in reference to the theme.
Among other events to mark the day included a ceremony at the Memorial Gates Commonwealth War Memorial in Hyde Park to commemorate the contribution of Commonwealth soldiers during the First and Second World War.