Zuckerberg said that the company hopes to launch the function soon, adding that Facebook does not want the new tool to allow a down-voting and up-voting system, like that of sharing site Reddit.
Now, users only have the option of "liking" friends' posts about news events like the refugee crisis or commenting about them.
"What they really want is the ability to express empathy. Not every moment is a good moment," Zuckerberg said.
Zuckerberg answered a range of other questions at the town hall event, including what kind of future he wanted for his expected daughter and the rising cost of healthcare.
In an answer to a question from an audience member about what is Zuckerberg's favorite emoji, the chief executive said his favorite sticker was the "cactus" and an image of his dog, Beast.