Although cognitive aptitude has been examined as an individual difference in second language acquisition (SLA; for overview, see Dörnyei and Ryan 2015), there is a dearth of research on the influence of learning disabilities (LDs) in second language (L2) learning for children. In fact, LDs are seldom researched as an influential individual difference in SLA for young bilingual children. Thus, this chapter will focus on a study that examined LDs as an individual difference in SLA for English learners (ELs), bi- and multilingual children who are acquiring English as an additional language in U.S. schools. In doing so, the study asks the following research questions: (1) What are the external individual differences (IDs) in the SLA of ELs with disabilities? (2) How do these external IDs contribute to internal IDs for ELs with disabilities? (3) In what ways do these individual differences represent deficit thinking? The study utilized a multiple case study design (Stake 2006) of two U.S. middle schools. The participating students were 11 ELs with LDs. The ethnographic data included 74 classroom observations; 53 interviews with students and staff; and school records. Data were analyzed through hybrid inductive-deductive coding (Fereday and Muir-Cochane 2006). For its theoretical underpinnings, the study utilized deficit thinking (Valencia 1997), which argues the underperformance of children is attributed to their supposed innate deficiencies, instead of external factors within schools. The analysis revealed the LDs of ELs were linked to limited L2 learning opportunities. As a result of their LDs, ELs were placed in classrooms where they were (a) isolated from their English-proficient peers, (b) restricted from collaborative language learning tasks, and (c) primarily exposed to behavior-management teacher discourse. Yet, ELs’ LDs - not the linguistically poor learning environments - were positioned by educators as the cause of ELs’ plateauing English proficiency. The study illuminates how individual differences in SLA for ELs with LDs are, in part, shaped by learning conditions in the school.