In 273/72 BC, she became queen of Ptolemaic Egypt upon her marriage to her brother, Pharaoh Ptolemy II Philadelphus, acquiring the royal name Arsinoe Philadelphos.

The marriage was for political reasons: both claimed the throne of Macedonia and Thrace (by the time of his death Lysimachus was ruler of both regions, and his power extended to southern Greece and Anatolia).

[15] She eventually left from Samothrace for Alexandria, Egypt, to seek protection from her brother, Ptolemy II Philadelphus.

[17] In Egypt, she is believed to have instigated the accusation and exile of Arsinoe I, the wife of her younger brother Ptolemy II.

[20] Her role as queen was unprecedented in the dynasty at the time and became a role model for later Ptolemaic queens: she acted alongside her brother in ritual and public display, became a religious and literal patron, and was included in the Egyptian and Greek cults created for them by her brother.

[21] Sharing in all of her brother's titles,[22] she was quite influential, having towns dedicated to her, her own cult (as was Egyptian custom), appearing on coinage, and contributing to foreign policy,[23] including Ptolemy II's victory in the First Syrian War between Egypt and the Seleucid Empire.

All temples in Egypt were required to include a cult statue of Arsinoe II alongside the main deity of the sanctuary.

In the relief at the top of the stele, Arsinoe is depicted among the deities receiving sacrifice from Ptolemy - an image that recurs throughout the country.

From 263 BC, a portion of tax on orchard and vineyard produce in each nome of Egypt was dedicated to funding the local cult of Arsinoe.

The holder of the office was included as part of the dating formula in all official documents until the late second century BC.

Every household along the procession's route was required to erect a small altar of sand and sacrifice birds and lentils for Arsinoe.

Similar sanctuaries were established at a number of port-cities under Ptolemaic control, including Citium in Cyprus, Delos in the Nesiotic League, and Thera.