Koch's longtime law partner James Gill says Saturday Koch's sister, Pat Thaler, sat in the same spot Koch regularly occupied in a front row pew Sunday.
Koch died of congestive heart failure in February at age 88.
Timothy Cardinal Dolan remembered the former mayor during his regular mass.
Gill says Koch loved attending mass and "loved being in that front row." Koch was a close friend of the late Cardinal John O'Connor and St. Patrick's held a seat at Midnight Mass for the mayor.
Gill says the event was meant to be an informal farewell, with no assigned seating.