The history of the church of San Iacopo in Altopascio changed in 1988, when the remains of an earlier worship building, dating from the late 11th century, were found. From these - which included part of the facade and apse - it can be deduced that the original temple was smaller in size than the one built in the second half of the 12th century. The beautiful crenellated bell tower can be dated accurately back to 1280.
In the second half of the 15th century, major restoration work was carried out, during which the roof of the church was replaced with a cross vault, the portal was redone, as well as the entire building was plastered again and the floor replaced. The opening of a door on the south side, decorated with colored marble, dates back to the 16th century. When the population of Altopascio grew between the 16th and 17th centuries, the baptismal font was made.
Between 1827 and 1830 – after the closure of the hospital ordered by Grand Duke Pietro Leopoldo – the church was rebuilt anew, its orientation was changed, and the medieval building was transformed into the transept of the new structure. The altar and pulpit were lost, the floor was removed, and the vaults were destroyed. Since then the building stands as we see it today, although in 1995, when the square in front of the ancient facade was re-designed, the complex was definitely redeveloped.