With more immigrants coming to New Zealand, more people hope their children maintain their mother tongue while they are living in the host country. Many language schools are catering for this need by providing courses in Chinese （L2）, taught either in English (L1) or in both English and Chinese. There is often disagreement in L2 acquisition research concerning which teaching method is better: to use L2 only or to use the learners’ L1 as an aid, especially for children who are living overseas. This descriptive study investigated two teaching methods in teaching children to learn L2 (Chinese) vocabulary, one using the children’s L2 (Chinese) only and the other using a combination of the children’s L2 (Chinese) and L1 (English). Differences were compared between the two methods in teaching some abstract and concrete vocabulary in both short-term and long-term memory. One teacher and twenty-seven students from two classes at the same proficiency level from the Chinese School of New Century Education Centre participated in this research. Results of ten immediate post-tests and one delayed post-test on the vocabulary from the lessons in the textbook were used as the data for analysing the short-term and long-term effectiveness of the two teaching methods. The results of the study reveal that the bilingual teaching method produced much better test results than the single language one in teaching children to learn vocabulary in their second language, particularly in the learning abstract words. Thus, it is strongly recommended that bilingual language teaching should be encouraged in second language (L2) teaching, especially when teaching children.