The current study examined the extent to which native speakers of North American and Singapore English differentially perceive the comprehensibility (ease of understanding) of second language (L2) speech. Spontaneous speech samples elicited from 50 Japanese learners of English with various proficiency levels were first rated by 10 Canadian and 10 Singaporean raters for overall comprehensibility and then submitted to pronunciation, fluency, vocabulary, and grammar analyses. Whereas the raters’ comprehensibility judgements were generally influenced by phonological and temporal qualities as primary cues, and, to a lesser degree, lexical and grammatical qualities of L2 speech as secondary cues, their linguistic backgrounds did make some impact on their L2 speech assessment patterns. The Singaporean raters, who not only used various models of English but also spoke a few L2s on a daily basis in a multilingual environment, tended to assign more lenient comprehensibility scores due to their relatively high sensitivity to, in particular, lexicogrammatical information. On the other hand, the comprehensibility judgements of the Canadian raters, who used only North American English in a monolingual environment, were mainly determined by the phonological accuracy and fluency of the L2 speech.