This study compared individuals from two first language (L1) backgrounds (Italian, Mandarin) to determine how they may differ in their perception of Japanese consonant length (i.e. singleton vs. geminate) according to the phonemic status of length in L1 and experience with Japanese. The participants included two groups of non-native learners of Japanese: 14 native Italian speakers (NI + Japanese), 18 native Mandarin speakers (NM + Japanese) and two control groups: 14 native Italian (NI -- Japanese) speakers naïve to Japanese, 10 native Japanese (NJ) speakers. The participants' length perception accuracy was examined in a forced-choice identification task. The NJ listeners hardly misperceived any tokens, but the non-native listeners were generally accurate (> 85%) in identifying the Japanese length category. The NI -- Japanese group was slightly (albeit non-significantly) more accurate than the NM + Japanese group, suggesting the possibility that the use of phonemic length in L1 was facilitative. The direction of misperception (i.e. singleton as geminate or geminate as singleton) differed according to different group. Non-native learners' results also provided evidence for plasticity in cross-linguistic perception in adulthood.