Mandarin speakers’ productions of English sentences, spontaneous speech, and filtered speech were rated for degree of foreign accent by native English and Mandarin listeners. Results showed Mandarin speakers with 12 years' length of residence (LOR) in the U.S. were rated to be accented as those with zero LOR. Untrained native Mandarin listeners with no LOR in the target language environment were comparable to native English listeners in gauging degree of foreign accent based on sentences and spontaneous speech. No stimulus effect was found between sentences and spontaneous speech for accent rating. Filtered natural speech appeared to attenuate degree of foreign accent and Mandarin listeners were not able to assess foreign accent based on long excerpts of filtered speech. The findings suggest that LOR is not an important predictor of degree of foreign accent for adult speakers with late age of arrival (AOA).