This study elicited and analyzed all the Chinese and English interrogatives from the Singapore Early Child Mandarin Corpus (132 children aged 2;6, 3;6, 4;6, and 5;6) to examine the effects and predictors of early bilingual development in Singapore preschoolers. The results indicated that: (1) there was significant age (but not gender) effect in the production of Chinese and English interrogatives; (2) relatively more types of English interrogatives were produced and more preschoolers produced English interrogatives; (3) Parent Language Input Pattern significantly predicted the increase of Chinese interrogatives, whereas Parent Language Input Pattern and Language Spoken by Child jointly but negatively predicted English interrogatives; (4) the pattern that both parents only speak Chinese was associated with the highest production of Chinese interrogatives and the lowest production of English ones, whereas the pattern that both parents only speak English had the highest production of English interrogatives; and (5) the 'one-parent-one-language' pattern was found to have a balanced but reduced production of Chinese and English interrogatives, indicating a subtractive bilingualism in Singapore preschoolers.