Counterfactuals are a type of conditional sentences used to convey situations that do not correspond to reality. Tense morphology is a core ingredient to encode counterfactuals in English and most Indo-European languages. Mandarin Chinese (hereafter Chinese) lacks tense morphology and does not require counterfactuals to be formally distinguished from other types of conditionals. In the past, this lack of obligatory and systematic counterfactual marking led scholars to hypothesize that Chinese native speakers (NSs) may have a diminished ability to reason counterfactually. Research involving NSs has eventually debunked this belief, unveiling the existence of specific linguistic strategies systematically used in Chinese counterfactual expression. However, no study has tested learners on either production or comprehension of Chinese counterfactuals. This study contributes to filling this gap by investigating how L1-English learners of Chinese-as-a-foreign-language (CFL) interpret and produce counterfactuals in Chinese by means of different linguistic strategies. To this end, a truth-value judgment task and a written sentence-completion task were devised and administered to 51 CFL learners and 29 Chinese NSs. The results revealed that both comprehension and production are modulated by foreign language proficiency, and the targeted linguistic strategies are mastered at different stages of acquisition, with differing patterns between comprehension and production. Furthermore, despite the fact that counterfactuals need not be overtly marked in Chinese and can be expressed and interpreted based on context and world knowledge, results indicated that in the absence of linguistic marking, most learners do not reach counterfactual interpretation. The qualitative examination of learners' task responses also suggested that L1-English partially influences the acquisition process of Chinese counterfactual expression, both in a facilitative and non-facilitative fashion. Lastly, the findings of this study confirmed that even if not explicitly taught, learners can eventually acquire the linguistic strategies used to express counterfactuals in Chinese. [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.]