This article discusses why and how English was able to turn into a contemporary Jewish language among Yiddish-speaking American Hasidic Jews, in marked contrast to Israeli Hebrew (IH), which has not been similarly adjusted. One reason is that communal attitudes towards English are not as ideologically charged as compared to the “zealous” opposition to IH. Another reason is that English is able to undergo phonological and lexical modifications that enable Hasidic English to function as an ethnolect used within the community. This process, however, is linguistically more complex for IH, which thus remains an outsider language among Israeli Yiddish-speaking Haredim. The outsider status of IH versus the insider status of Hasidic English is reflected in the code-switching patterns attested among Yiddish public speakers, resulting in a common and effortless pattern of Yiddish-English switching among American speakers, as opposed to rare and marked instances of switches to IH among Israeli speakers.