The settlement was first mentioned in a 1191 deed issued by Archbishop Adalbert (Vojtěch) of Salzburg, when the local Carinthian counts Hermann I and Otto II of Ortenburg had a hospital (Spittl) with a chapel built where the ancient road leading to the Katschberg Pass and Salzburg crossed the Lieser river. The adjacent settlement received market rights in 1242. Together with the Ortenburg estates, Spittal in 1418 was inherited by Count Hermann II of Celje. The Counts of Celje, raised to immediate Reichsgrafen in 1436, became extinct when Count Ulrich II was killed by the liegemen of László Hunyadi in 1456, after which the Habsburg emperor Frederick III, also Duke of Carinthia, seized his territory. Federick granted the citizens the right to choose their own judge and the council. However, Spittal and the surrounding lands were devastated by Turkish warriors in 1478 and shortly afterwards occupied by the Hungarian troops of Emperor Frederick's long-time rival King Matthias Corvinus. Further ravaged by a peasant's revolt and two fires in 1522 and 1729, the decline continued, until in 1524 Archduke Ferdinand I of Austria entrusted his treasurer Gabriel von Salamanca (1489–1539) with the former Ortenburg county.
From 1533 onwards, the Counts of Salamanca-Ortenburg had Schloss Porcia erected on the main square as their residence. The building in the style of an Italian palazzo is considered one of the most important Renaissance castles in Austria. They also rebuilt the Spittl hospital on the other side of the Lieser River and the late Gothic Catholic parish church of Mary's Annunciation upon Romanesque foundations of the 13th century. In 1662 Spittal passed to the Gorizia Counts of Porcia, owners of Schloss Porcia until 1918. Today the palace hosts an annual festival for classic theatrical comedies (Komödienspiele Porcia) and is also home of a museum of local history. In 1537 the Carinthian Khevenhüller noble family had a residence erected opposite the
