William Woodthorpe Tarn and numismatist Robert Senior place Antimachus as a member of the Euthydemid dynasty and probably as a son of Euthydemus and brother of Demetrius.

Eumenes and Antimachus could be his heirs; it was standard for Ptolemaic and Seleucid kings to include their sons as joint regents, with variable formal or actual power.

This document was found near Bactra in Northern Afghanistan and reads:[2] "Βασιλεύοντος Ἀντιμάχου ἔτους τριακοστοῦ [μηνὸς - - ] ... ἐν Ἀμφιπόλει τῇ πρὸς τῇ Κ ἀρελοτηι εἰσηγεῖτα[ι - - τῶν] ... ξένων μαν ηερχολλ μηνον ... τῶν τεσσαρά[κοντα - - - ] ... Σκυθῶν ἀργυρίου ἐπισήμου δραχμῶν ἑκατὸν ... μενοῦ πλήθους τοῦ ἀργυρίου [ - - - ] ...." "In the reign of Antimachos in the year 30 [month + day] in Amphipolis near K[]arelote has introduced ... of the... mercenaries (?)

sum of money ...."Antimachus I issued numerous silver coins on the Attic standard, with his own image in a flat Macedonian kausia hat, and on the reverse Poseidon with his trident.

[3]Antimachus I also issued round bronzes depicting an elephant on the obverse, with a reverse showing the Greek goddess of victory Nike holding out a wreath.