This chapter provides an overview of the foreign-born population in the United States, comprised of documented and undocumented immigrants, refugees, and asylum-seekers. This population has more than quadrupled since the 1960s, with over 44 million in 2017, and expectations to double by 2065. The main reasons for migration include escaping from poverty, seeking a higher quality of life, and political unrest. Immigrants, refugees, and asylum-seekers may experience a number of atrocities like war, torture and killing, sexual assault, incarceration, and threats of death throughout their pre-migration and migration experiences. Post-migration factors such as cultural and acculturation issues, language, and barriers to physical and mental health treatment support or hinder their adjustment and resettlement in the United States. The information and experiential activities provided in this book chapter focus on (a) facilitating a deeper understanding of characteristics that inform the experiences of immigrants, refugees, and asylum-seekers; (b) individual and systemic factors that impact their entire migration experience and adjustment; and (c) implications for clinical practice with a social justice perspective to guide assessment, diagnosis, and intervention with this population.