The Single Ladies singer, who now has long braided locks, appears in the clip to highlight the event and urge people to "do one thing for another human being".
Beyonce, 30, will mark the day - 19 August - by filming a live music video in New York's General Assembly Hall for the new ballad 4, which will be released in aid of the cause.
People are asked to post messages online about the good deeds they have done for others, before a single message of hope is released to 1 billion people.
Beyonce says: "We all see the headlines, and we think: 'What can I really do to help?'"
In a statement, Beyonce said: "World Humanitarian Day is an opportunity for all of us to work together to make a difference.
"This is our time to leave our mark on the world and show that we were here and we care."
To show your support, visit: www.whd-iwashere.org/
Will you be marking World Humanitarian Day? Tell us in our comments box below.
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