He is first mentioned as being present with his uncle at the siege of Nora in 320 BC, when he was given up to Eumenes as a hostage for the safety of the latter during a conference with Antigonus. At a later period we find him entrusted by his uncle with commands of importance. Thus in 315 BC, when Antigonus was preparing to oppose the formidable coalition organized against him, he placed Ptolemy at the head of the army which was destined to carry on operations in Anatolia against the generals of Cassander.
The young general successfully carried out his mission, thereby relieving Amisus, which was besieged by Asclepiodorus, and recovered the whole satrapy of Cappadocia; after which he advanced into Bithynia, compelling king Zipoites to join his alliance. Upon his approach and occupation of Ionia, Seleucus withdrew from that territory. 
In the latter part of that year, Ptolemy next threatened Caria, which was defended for a time by Myrmidon, the Egyptian general; but in the following year (314 BC) Ptolemy was able to strike a decisive blow in that quarter against Eupolemus, the general of Cassander, whom he surprised and totally defeated.
In the summer of (313 BC), the arrival of Antigonus himself gave a decided preponderance to his arms in Anatolia, and Ptolemy, after rendering active assistance in the sieges of Kaunos and Iasus, was sent with a considerable army to Greece to carry on the war there against Cassander. His successes were at first rapid: he drove out the garrisons of his adversary from Chalcis and Oropus, invaded Attica, where he compelled Athens' tyrant Demetrius Phalereus to make overtures of submission, and then carried his arms triumphantly through Boeotia, Phocis, and Locris. Wherever he went, he expelled the Macedonian garrisons, and proclaimed the liberty and independence of the cities.
He then directed his armies to the Peloponnese, where the authority of Antigonus had been endangered by the recent defection of his general Telesphorus. Here he appears to have remained till the peace of 311 suspended hostilities in that region.
He is thought to have considered that his services had not met with their due reward from Antigonus; and therefore, when in 310 BC the kings of Macedonia and Egypt were preparing to renew the war, Ptolemy suddenly abandoned the cause of his uncle and concluded a treaty with Cassander and Ptolemy I Soter. His ambition may have been to establish himself in the chief command in the Peloponnese: but the reconciliation of Polyperchon with Cassander must have frustrated this: and on the arrival of the Egyptian king with a fleet at Cos, Ptolemy repaired from Chalcis to join him. He was received at first with the utmost favour, but soon gave offence to his new patron by his intrigues and ambitious demonstrations, and was in consequence thrown into prison and compelled to put an end to his life by poison, 309 BC.
- Smith, William (editor); Dictionary of Greek and Roman Biography and Mythology, "Ptolemaeus (7)", Boston, (1867)
This article incorporates text from a publication now in the public domain: Smith, William, ed. (1870). "article name needed". Dictionary of Greek and Roman Biography and Mythology.