Why do immigrants often concentrate in low-wage workplaces with high shares of minority employees? Is workplace segregation relative to natives declining among native-born descendants of immigrants—who often achieve higher acculturation and socioeconomic progress—compared to the immigrant generation? Using rich linked employer-employee administrative data from Norway, we show that, on average, 37% and 24%, respectively, of immigrants’ and their descendants’ coworkers have immigrant background compared to 9% among natives. For economic segregation, the percentile rank of coworkers’ salary is, on average, 36, 50, and 52 for immigrants, descendants, and natives, respectively. Using information on characteristics of employees, workplaces, and residential neighborhoods, a formal decomposition shows that these factors collectively explain 33-68% and 78-80% of ethnic and socioeconomic workplace segregation, respectively, for both immigrants and their descendants. Within both generations, workers’ education and labor market attainments, industry of employment, and share of immigrant neighbors contribute most to workplace segregation relative to natives. Overall, our findings reveal a sharp decline in workplace segregation across immigrant generations, where the second generation gain improved access to workplaces in the mainstream economy.