This study examined the extent to which socioemotional well-being mediated the relationship between language status and achievement, while exploring variability in this relationship based on informant (student versus teacher reports of socioemotional problems) and native language background (Spanish-speaking English language learners [ELLs] versus ELLs from Asian-language backgrounds). Participants included 9,046 fifth-grade students from the Early Childhood Longitudinal Study-Kindergarten Cohort of 1998. Results from structural equation modeling showed that Spanish-speaking ELLs reported more social-emotional problems as compared to English-monolingual (EM) and Asian-language ELL classmates in third grade, which partially explained their lower achievement levels in fifth grade. The model accounted for approximately 34% of the variance in students' academic achievement in fifth grade (R[superscript 2] = 0.343, p < 0.001). When comparing ELL and EM students, results differed when using teachers' versus students' reports of socioemotional well-being. For both Spanish-speaking and Asian-language ELLs, teachers perceived fewer social and emotional difficulties than the students themselves reported in comparison to their EM classmates.