Although children's use of speech registers such as Baby Talk is well documented, little is known about their understanding of Foreigner Talk, a register addressed to non-native speakers. In Study 1, 4- to 8-year-old children and adults (N = 125) heard 4 registers (Foreigner Talk, Baby Talk, Peer Talk, and Teacher Talk) and predicted who would receive each. By 5 years, children selected the target addressee of Foreigner Talk above chance. In Study 2, 5- to 8-year-old children and adults (N = 94) completed a register match task manipulating 3 addressee cues: language, appearance, and origin. Prior to 7-8 years of age, children did not use the language cue alone when identifying the addressee of Foreigner Talk, and at no age did children use one cue more than another. In contrast, adults made use of language and appearance more than the origin cue. These findings suggest that an understanding of Foreigner Talk emerges by school age yet also undergoes developmental change.