The Byzantine economy was among the most robust economies in the Mediterranean and the world for many centuries. Constantinople was a prime hub in a trading network that at various times extended across nearly all of Eurasia and North Africa. It could be argued that up until the 7th century, the Eastern Roman Empire had the most powerful economy in the world. The Arab conquests, however, would represent a substantial reversal of fortunes contributing to a period of decline and stagnation. The Byzantine state restructured its administrative and fiscal systems, introducing the theme system, which organized land and military service in a way that ensured both local defense and agricultural productivity. Rural life revived as new lands were brought under cultivation, and local economies became more self-sufficient, reducing dependence on long-distance trade that had been curtailed by the loss of eastern territories. By the 9th and 10th centuries, the empire experienced a notable resurgence: agricultural output increased, population levels rose, and the circulation of coinage expanded once again. However, by the 12th and 13th centuries, the economic balance began to shift. Western maritime republics such as Venice and Genoa gradually overtook Byzantine merchants, largely due to the tax exemptions and trading privileges granted to them under the Komnenian emperors. This process accelerated after the Fourth Crusade and the establishment of the Latin Empire, during which Venetian traders gained control over key ports and commercial networks once held by the Byzantines. The Byzantines continued to face economic challenges during the Palaiologan era until its fall in 1453.

One of the economic foundations of the empire was trade. The state strictly controlled both the internal and the international trade. It has been argued by the historian Alex M. Feldman that this amounted to an early version of the political economy of mercantilism. Constantinople remained the single most important commercial centre of Europe for much of the Medieval era, which it held until the Republic of Venice slowly began to overtake Byzantine merchants in trade; first through tax exemption under the Komnenoi, then under the Latin Empire.

From 4th to end of 6th century the eastern part of Roman Empire had demographic, economic and agricultural expansion. The climate was opportune for farming. Even in marginal regions rural settlements flourished. The Arab conquests of the 7th century and subsequent territorial losses disrupted traditional agricultural regions, particularly in Egypt and the Levant, leading to a decline in surplus production and forcing the empire to rely more on Anatolia and the Balkans. During the middle Byzantine period, agricultural recovery occurred alongside political stabilization. Reforms encouraged small-scale farming, irrigation, and improved crop techniques. Large estates still existed, but many peasants gained more autonomy, and the production of olive oil, wine, and cereals expanded to meet both domestic and trade demands.

The 12th century saw the development of tilling and milling technologies in the West, but there is less evidence for similar Byzantine innovation. Western advances like the windmill were adopted by the Byzantines, but, unlike the West, Arabic numerals were not yet implemented for double-entry book-keeping. There are illustrations of agricultural implements from illuminated medieval manuscripts of Hesiod's Works and Days including the wheel, mortar, pestle, mallet and some parts for carts and soleard plough, but, even centuries later, neither the plough nor wheeled cart were widely in use, possibly because of the nature of the Pontic terrain.

In the late Byzantine period (13th–15th centuries), after the Latin occupation and territorial fragmentation, agriculture faced new challenges. Estates were often overtaxed, and warfare or raids disrupted rural life. Despite this, certain regions, particularly in western Anatolia and parts of Greece, remained productive, supplying local markets and urban centers. Throughout Byzantine history, agriculture remained the foundation of the empire’s economy, adapting to political and environmental pressures while sustaining urban populations, the military, and long-distance trade.

The Eastern Roman economy suffered less from the Barbarian raids that plagued the Western Roman Empire. Under Diocletian's reign, the Eastern Roman Empire's annual revenue was at 9,400,000 solidi, out of a total of 18,000,000 solidi for the entire Roman Empire. These estimates can be compared to the AD 150 annual revenue of 14,500,000 solidi and the AD 215 of 22,000,000 solidi. By the end of Marcian's reign, the annual revenue for the Eastern empire was 7,800,000 solidi, thus allowing him to amass about 100,000 pounds/45 tonnes of gold or 7,200,000 solidi for the imperial treasury. Warren Treadgold estimates that during the period from Diocletian to Marcian, the Eastern Empire's population and agriculture declined a bit, but not much. Actually, the few preserved figures show that the largest eastern cities grew somewhat between the 3rd and 5th centuries. By Marcian's reign the Eastern Empire's difficulties seem to have been easing, and the population had probably begun growing for the first time in centuries. The period encompassing Anastasius' and the first half of Justinian's reign saw further economic expansion, with state revenues increasing and a decline in land abandonment and complaints of overtaxation. Such growth would also explain the other signs of public and private prosperity at the time, including Justinian's ability to undertake so many costly activities at once.

The wealth of Constantinople can be seen by how Justin I used 3,700 pounds/1.66 tonnes of gold just for celebrating his own consulship. By the end of his reign, Anastasius I had managed to collect for the treasury an amount of 23,000,000 solidi or 320,000 pounds/144 tonnes of gold. At the start of Justinian I's reign, the Emperor had inherited a surplus 28,800,000 from Anastasius I and Justin I. Before Justinian I's reconquests the state had an annual revenue of 5,000,000 solidi, which further increased after his reconquests in 550. At the height of Justinian's reign in 540 (before the plague), the state revenues of the Byzantine Empire were estimated to be as high as 11.3 million solidi. Due to the empire's affluence, Justinian was able to undertake costly building projects. The church of the Holy Apostles in Constantinople and the church of Saint John at Ephesus likely cost 1 million solidi each, and the Perpetual Peace with Persia cost 792,000 solidi. Nevertheless, Justinian I had little money left towards the end of his reign partly because of the Justinian Plague, and the Roman–Persian Wars (Justinian spent large amounts of money in annual subsidies to the Sassanian Empire), as well as his wars of reconquest in Italy and North Africa, all of which greatly strained the royal treasury. In addition to these expenses, the rebuilding of Hagia Sophia cost 20,000 pounds/9 tonnes of gold. Subsidies to enemy states were also paid by Justinian's successors: Justin II was forced to pay 80,000 silver coins to the Avars for peace; his wife Sophia paid 45,000 solidi to Khosrau I in return for a year's truce, and then Tiberius II Constantine gave away 7,200 pounds of gold each year for four years, on top of giving away the treasure of Narses and 1,000 centenaria to the poor (allegedly worth 100,000 pounds of gold). The East Roman Empire's aristocratic language of Latin began to erode and give way to the native language of Greek starting during the Roman-Persian Great War of 602-628, the solidus (plural: solidi) would begin to also be known by its Greek name, the nomisma (plural: nomismata). For all of the financial difficulties the empire faced, the government kept its revenues at a remarkably high level under the circumstances and was able to pay their soldiers. The government would have been functioning at a high level of efficiency to handle its fiscal problems well and avoid financial collapse and bankruptcy.

However, after the deposition of Maurice and the ascension of Phocas to the throne, the empire's financial situation worsened. During the final Byzantine Sassanid War, Egypt, Syria and Byzantine Mesopotamia were lost to the Persians, and these territories must have made up more than half of the empire's total revenues. Heraclius was able to avert bankruptcy through unprecedented borrowing from the church, substantially reducing state salaries and melting down statues in order to pay the empire's soldiers. Although Heraclius regained those territories following his victory in the war, the Arabs would conquer those territories a few years later.