Mandarin:
* Simplified: 贾斯汀·比伯 (Jiǎsītīng Bǐbó)
* Traditional: 賈斯汀·比伯 (Jiǎsītīng Bǐbó)
Cantonese:
* Jyutping: gaa2 si1 ting1 bei2 bo1
* Yale: gaa2 si1 ting1 bei2 bo1
Notes:
* The romanized spellings above are just approximations of the pronunciation. The actual sounds will depend on your pronunciation of Mandarin or Cantonese.
* The "·" symbol separates the two names.
* In Chinese, surnames usually come before given names.
Other Considerations:
* You could also use a transliteration system like pinyin or Wade-Giles, but these might not be as widely understood.
* You could ask a native speaker for help in saying the name correctly.
Let me know if you need any further help!