Chandragupta's son, Bindusara Maurya, expanded the realm to the south and sealed alliances with the Tamils and the Cholas. When Chandragupta's grandson, Ashoka (268-232), came to the throne, the Maurya Empire stretched from the Zagros Mountains to the Brahmaputra River

The appearance of new ideas in the Mauryan period is reflected in various descriptions of King Bimbisara of Magadha and Emperor Ashoka. The former was referred to as the "pradesha king", i.e., king of a small territory or province, while Ashoka was regarded as the "omnipotent ruler of Jambudvipa", i.e., the whole of India. It is the edicts of the emperor that provide the main evidence with regard to the extent of the Mauryan empire. Some information is also to be gleaned from classical authors writing of the age of Chandragupta. Information provided by Chinese travellers also has some value, particularly when it is borne out by epigraphic or archaeological evidence.

Definition of the western borders of the empire has been greatly facilitated by the discovery in Kandahar—the centre of Arachosia—of the edicts of Ashoka (Greek and Greco-Aramaic inscriptions), which clearly points to the fact that Arachosia (now an area of modern Afghanistan) was part of his empire. In Ashoka's edicts there are several references to the Yonas and Kambojas as peoples living in the west of the country. The word Yonas is used to refer to Greeks, whose settlements were to be found in Arachosia. It was for the Greek population that versions of Ashoka's edicts were prepared in Greek. Some scholars hold that the Yonas in Ashoka's day were descendants of those Greek tribes which had settled in Arachosia at the time of Alexander of Macedon.

In Arachosia there also lived the Kambojas (an Iranian-language tribe), mentioned in ancient Indian legends as splendid horsemen and horse-breeders. The language of the Kambojas is hardly known, but because in the Aramaic version of Ashoka's edict from Kandahar we find many Iranian words, there is reason to believe that this version had been intended for the Kambojas. An edict of Ashoka's was also found in Lampaka (near modern Jelalabad) which confirmed that Paropamisus actually was part of the Mauryan empire (this had only been gleaned before that from Greek sources telling of the results of the armistice between Chandragupta and Seleucus).

Data found in the Kashmir chronicle Rajatarangini and in descriptions by Chinese pilgrims give us reason to believe that part of Kashmir was also incorporated into Ashoka's empire. Tradition asserts that Shrinagar, the main city of Kashmir, was built in the reign of Ashoka. Some parts of Nepal also may have been within the confines of his empire. Epigraphic findings and written sources also indicate that Bengal was part of the empire. When edicts issued by Ashoka were found in Southern India this facilitated the establishment of the empire's southern borders. It ran approximately south of the modern Chitaldrug district. In the south this empire bordered with the states of the Cholas, Keralaputras and Satyaputras, mentioned in Ashoka's edicts as territories outside his state.

However the Mauryans maintained close contacts with these regions. Buddhist stupas were built there, and teachers were sent as well. Diplomatic links were also maintained with many other countries, including the Hellenistic countries to the west of India, with Sri Lanka and certain regions of Central Asia.