Antiochus III launched a campaign to regain control of the eastern provinces, and after defeating the Parthians in battle, he successfully regained control over the region. The Parthians were forced to accept vassal status and now only controlled the land conforming to the former Seleucid province of Parthia. However, Parthia's vassalage was only nominal at best and only because the Seleucid army was on their doorstep. For his retaking of the eastern provinces and establishing the Seleucid borders as far east as they had been under Seleucus I Nicator, Antiochus was awarded the title great by his nobles. Luckily for the Parthians, the Seleucid Empire had many enemies, and it was not long before Antiochus led his forces west to fight Ptolemaic Egypt and the rising Roman Republic.

The Seleucids were unable to further intervene in Parthian affairs following the Seleucid defeat at Magnesia in 190 BCE. Priapatius (r. c. 191–176 BCE) succeeded Arsaces II, and Phraates I (r. c. 176–171 BCE) eventually ascended the Parthian throne. Phraates I ruled Parthia without further Seleucid interference.