In the 1930s Stein organised four archaeological expeditions to Iran. He was a student of Iranian studies and at the end of his third Central Asian expedition he had already visited its eastern borders with Afghanistan. He knew well the events and places connected with Alexander the Great’s conquest of Persia, and had encountered Iranian influences in written documents and artefacts while on the eastern Silk Road.

In January 1932 he visited Persian Baluchistan and travelled to Kerman. For this short expedition he employed a Hungarian assistant, the young Indologist Károly Fábri (1899-1968). In September he set off again for Iran, and during his second expedition from 1932 to 1933 he continued his explorations along the Persian Gulf, passing through Minab, Hormuz, Bandar Abbas, and the costal area of Laristan to Bushire. On his third expedition (1933-1934) he travelled through eastern Fars, while the fourth Iranian expedition (1935-36) took him from western Fars to Iranian Kurdistan. During these expeditions, he excavated sites dating from the Neolithic to the Islamic period.

As he had discovered the Han-dynasty limes (border defenses) in Gansu, he had a keen interest in the researches of Fr. Antoine Poidebard (1878-1955), the pioneer of aerial archaeology, in respect of the Roman limes in Syria. Stein decided to make similar investigations in Iraq and the Transjordan. In 1929 and 1935 he took some short flights in R.A.F. aeroplanes, and realized the great value of aerial surveys. Therefore from 1938 to 1939 he made ground and aerial surveys from the Tigris in north-eastern Iraq to the Gulf of Aqaba. The remains of Roman highways, aqueducts, bridges, cisterns and milestones were discovered using this new technology.