Emanuel also spoke to the group about the importance of community colleges Friday morning.
He attended a gathering of Mayors for Freedom to Marry.
On Thursday in Chicago, Emanuel said he was going the support the group's aims because he thinks it is the right thing to do and is consistent with the nation's values.
"To me, marriage is the recognition of love and the state should not be in the business of discrimination," Emanuel said.
According to organizers of Mayors for Freedom to Marry, more than 75 mayors have pledged to support same-sex marriage.