In this paper we quantify the effects of immigration on wages, employment, fiscal outcomes, and native welfare in a general equilibrium model with search and matching frictions and government redistribution. Immigration affects labor supply and productivity, firms’ job-creation incentives, and and interacts with fiscal systems that differ in both size and progressivity. The model features skill heterogeneity, capital accumulation, and high-skill–augmenting technology, allowing immigration to operate through multiple interacting channels.The framework is calibrated to 17 OECD economies using harmonized data for the 2015–2019 period on wages, unemployment, immigrant–native gaps, skill composition, and fiscal aggregates. We conduct comparative statics exercises that vary both the size and the skill composition of immigration flows. Welfare effects are highly heterogeneous across countries and scenarios, reflecting differences in job-creation responses, production complementarities, and fiscal adjustment. We show that tax progressivity and government size play distinct roles: progressivity redistributes the fiscal consequences of immigration across skill groups, while government size mainly scales aggregate fiscal effects. Overall, the results highlight that the welfare impact of immigration cannot be inferred from skill composition alone, but depends critically on labor market frictions, production structure, and design of taxation and redistribution.