Church of St. Sigismund was built in 1431-1432 at the site of an earlier wooden temple. The founder of the new building was Dobieslaw Oleśnicki and his wife, Katarzyna. The building was consecrated by cardinal Zbigniew Oleśnicki, bishop of Cracow in 1442. In the 16th century the church was converted into a Calvinist church. In the sixteenth century, during the Polish-Swedish war the building suffered serious damage. In the 18th century, thanks to the efforts of the parish priest Szembek, the church was renovated and restored to the Catholics. In 1915, during the First World War, the church was severely damaged, among others, the vault in the nave and partly in the chancel was destroyed. In 1930 the church was rebuilt under the supervision of the architect Oskar Sosnowski.
The church consists of a four-bay nave and a two-bay, five-side ended chancel. To the chancel from the north adjoins the vestry with the treasury on the upper floor. Outside the church is covered with buttresses, and the facades at the base of windows are decorated with friezes. The western gable is filled with lancet blendes. The interiors of the church illuminate the pointed windows. The chancel is covered with a cross-rib vault on polygonal corbels. There is a pointed portal that leads from the chancel to the sacristy. In the chancel there is an erection plaque with bas-relief dating back to the middle of the 15th century.
Architektura gotycka w Polsce, red. T. Mroczko i M. Arszyński, Warszawa 1995.
Website zabytkowekoscioly.net, Sienno, kościół św. Zygmunta.