[5][6] Upon the outbreak of war, Seleucus commanded his own force, unsuccessfully besieging Pergamon,[7] and taking the city of Phocaea[8] before fighting in the Battle of Magnesia alongside his father.

[11] As part of the treaty, Seleucus oversaw the supply of grain and scouts to Roman and Pergamene forces during their campaign against the Galatians.

He renewed an alliance with the Achaean League,[12] and almost joined in Pharnaces I's invasion of Galatia, before reconsidering and turning back.

In 2 Maccabees 3, Seleucus IV sends out Heliodorus on a tax-collecting mission after hearing an inflated report of the Temple's wealth.

Seleucis IV appears to have run a fairly quiet period of rebuilding, but he managed relations with Rome astutely given the inferior position the Seleucid Empire found itself in after its defeat in the Roman–Seleucid War.