Emanuel, who began his fast Thursday at a mass honoring the feast of Our Lady of Guadalupe, said his action was part of a broader effort to make Congress realize that immigration reform is something Americans want, the Chicago Tribune reported Friday.
"For us it is essential to remind the United States Congress that there is support for immigration reform throughout the country," he said before placing roses in front of the church's statue of Our Lady of Guadalupe. "And we are going to fast and share in that effort in solidarity ... with those in Washington."
Chicago Aldermen Daniel Solis, Rey Colon and Lona Lane, who also attended the mass, said they would fast as well.
Emanuel, who is Jewish, said he would go without food from 7 p.m. Thursday until 7 p.m. Friday.
In Washington, backers of immigration reform have been taking turns fasting on the National Mall since November in an effort to urge Congress to approve an immigration bill.
Among Democrats within the Illinois congressional delegation, Sen. Dick Durbin announced he would fast from Thursday to Friday, Rep. Tammy Duckworth said she would fast for a day and Rep. Jan Schakowsky said she fasted last month.