In the IV century B.C. Ancient Greece entered a period of a crisis. The first evidence of it was a spread of mercenaries. Not only ordinary soldiers became mercenaries, but the generals as well. They entered service not only in other Greek cities, but also in the neighboring states. The article examines the main examples of the foreign service of Athenian generals. The author highlights two variants of service. A general could join the military service of the other state’s ruler for his personal aims without getting his fellow citizens’ approval. The foreign service of the generals could also contribute to strengthening relations between Athens and a ruling employer. The author brings under close study the activities of the general Iphicrates. We give a broad description of the relationship between the Thracian rulers and the Greek mercenary general and analyze the reasons which brought Iphicrates into entering into the Odrysian Kingdom service after 386 B.C. The author attempts to define the circumstances of the epoch when the Athenian general was adopted by Macedonian king Amynta III. We also analyze the conditions of the foreign service of the Athenian generals Chabrias (Egypt), Timotheus and Chares (Persia).