Growing up in the digital era, young children are exposed to numerous educational applications and programs, some with well-designed curricula and others focused more on entertainment or game-like qualities. With the increasing popularity of mobile language-learning applications among young children, this dissertation raises a crucial question: do these learning materials actually enhance children's acquisition of language? A total of 71 preschool-aged Mandarin-speaking children (M[subscript age] = 5.76, SD[subscript age] = 0.59) participated in a one-week-long intervention study in Nanjing, China. Across a total of two visits, we assigned children to two experimental conditions to watch targeted English-learning animations focusing first on verbs, in one condition, and on possessives in the other. Children from each condition were encouraged to watch their condition-related animations as many times as they wanted between visits, along with a new take-home animation that was neither verb- nor possessive-focused. Children's performance on target verb and possessive items (vocabulary and grammar) for both comprehension and production was measured after each animation viewing session, in addition to assessing general English verb tense and possessive marking. Overall, our results suggest that preschool-aged Mandarin-speaking L2 learners can benefit from targeted English-learning animations. Moreover, consistent with first language acquisition results in both English and Chinese, some target language categories appear to be easier to acquire than others (e.g., possessive grammar -'s > verb past tense grammar). In addition, comprehension measures for both vocabulary and grammar appear to be easier than production measures. Finally, our results demonstrate that standardized English tests that reflect children's general language knowledge might not be sensitive enough to capture children's limited exposure to targeted language-learning materials. Moreover, different amounts of exposure might be acquired for successful learning of different target language categories in L2 depending on their difficulty (e.g., easy L1 to L2 transfer facilitated learning of possessive -'s marking among Mandarin-speaking children). These findings not only demonstrate the potential for well-designed language-learning applications, and they also speak to a number of limitations, challenges, and future directions in how we might examine the efficacy of language-learning media. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]