Résumé : This thesis aims to address the following key question: “What affects immigrants to acquire capital and how is it generated?” This can be addressed by the following: (1) identifying micro-level determinants of immigrant language acquisition and integration; (2) assessing macro-level effects and micro-macro joint effects on immigrant language acquisition; and (3) reassessing the overall empirical findings based on theoretically derived micro-macro interactive mechanisms in the integration process. The research literature concerned with the determinants of immigrant/second language acquisition is reviewed to bring classic theories and models from economics and psychology together and initiate the construction of an economic-psychological modeling frame for immigrant language acquisition. Based on the modeling frame, an empirically testable model of immigrant language acquisition is formulated to identify the determinants of destination language proficiency. Furthermore, conceptually locating immigrants’ integration outcomes as the consequences of their language acquisition in a theoretical modeling framework, a model of immigrant integration is devised with three sub-models: (1) a model of immigrant economic integration; (2) a model of immigrant citizenship acquisition; and (3) a model of immigrant political integration. The models are tested using OLS regression and data from the Multicultural Democracy and Immigrants’ Social Capital in Europe: Participation, Organisational Networks, and Public Policies at the Local Level (LOCALMULTIDEM). Analysis results suggest that the economic model is robust in predicting immigrant language acquisition and integration outcomes. Educational attainment is found to be the most critical and consistent predictor of outcomes across cities and empirical models. Although the psychological model has relatively weak power in explaining the variation in language proficiency, the presumed mediating effect via attitudinal factors is detected in some cases. However, such mediation effect is barely identified in the sub-models of immigrant integration with an exception of political integration. Destination language proficiency is found to be the most consistent mediator that positively influences all of the integration outcomes. In the concluding chapters, further analyses and (re)interpretations are conducted as an overarching summary of the multivariate regression analyses to examine the role of institutions and propose a micro-macro integrative model that could suggest options for institutional design and directions for future research.