Models of cross-language perception suggest that listeners’ native language plays a significant role in perceiving another language, and propose that listeners assimilate non-native speech sounds to similar sounds in their native language. In this study, the effect of native language on the perception of Mandarin tones by Swedish learners is examined. Swedish learners participated in an identification task, and their performance was analyzed in terms of accuracy percentages and error patterns. The ranking of difficulty level among the four lexical tones by Swedish listeners differs from that found among English native listeners in previous studies. The error patterns also reveal that Swedish listeners confuse Tone 1 and 2, Tone 3 and 4, and Tone 2 and 4, the first two pairs rarely being confused by English listeners. These findings may be explained with the assimilation account: Swedish learners assimilate Tone 3 and 4 to Swedish pitch accents, thus they exhibit a unique pattern when perceiving the tones in Mandarin.