Which countries contributed the largest shares of undocumented migrants apprehended at the US southern border in 2025?

1. The headline: Mexico remained the single largest source in 2025

Public CBP reporting and multiple analysts treating FY2025 data show Mexico as the largest single country of origin for people apprehended at the U.S. southwest border, a pattern that reflects geography and long‑term trends in CBP encounter data ^{[5] [6] [2]}. CBP’s monthly updates for 2025 document dramatic month‑to‑month declines in raw apprehensions—February 2025 alone recorded 8,347 USBP apprehensions between ports of entry, a 94% drop from the prior year month—yet CBP and border analysts still report Mexicans as the leading nationality among those apprehended ^{[1] [5]}.

2. The next largest cohort: the Northern Triangle as a bloc — El Salvador, Guatemala and Honduras

Multiple data summaries and reporting identify the three Central American states commonly called the Northern Triangle as the next largest source of migrants after Mexico; Statista notes that in recent years roughly a third of non‑Mexican apprehensions came from El Salvador, Guatemala and Honduras, and migration analysts agree that these countries have historically accounted for a large share of non‑Mexican encounters ^{[3] [4]}. WOLA and other analysts emphasize that, even as flows diversify, the Northern Triangle remains a dominant regional contributor to southwest‑border apprehensions ^{[2] [6]}.

3. Rising diversity: South America, the Caribbean and “other” countries increased their share

Observers and think tanks documented an important shift in the early 2020s: more than half of irregular encounters began to originate beyond Mexico and the Northern Triangle, with growing numbers from South America (Venezuela, Colombia), the Caribbean (Cuba, Haiti) and even African nations traveling through Central America; the Wilson Center and Migration Policy analyses dramatize that diversification, noting thousands of arrivals from outside the immediate region in recent fiscal years ^{[4] [7]}. Statista and PBS analyses also highlight that non‑Mexican flows expanded substantially post‑2020, meaning the second tier of countries in 2025 included a broader set of origins than in past decades ^{[3] [7]}.

4. Quantities: FY2025 totals, and why precise country shares are hard to pin down from available sources

CBP’s FY2025 Border Patrol total for crossings between ports of entry was reported around 237,000–238,000 apprehensions, a steep decline from 2024 totals, and CBP’s monthly bulletins show dramatic month‑to‑month fluctuation in 2025 ^{[2] [8] [1]}. The available press sources establish clear rankings—Mexico first, the Northern Triangle collectively next, and rising flows from South America and elsewhere—but none of the supplied documents delivers a single, definitive country‑by‑country percentage table for the entire 2025 fiscal year that would permit exact share assignments for every country; therefore the description above reflects the best synthesis of the supplied reporting rather than a new tabulation ^{[1] [2] [3] [4]}.

5. Political framing, data limits and competing narratives

Domestic political actors and oversight committees use the same encounter data to advance differing narratives: some emphasize the “diversity” and humanitarian drivers of migration while others amplify security and enforcement concerns, and partisan briefs sometimes present aggregate encounter numbers as synonymous with successful entries rather than processed removals or expulsions—an important distinction highlighted by fact‑checking outlets ^{[9] [10]}. Analysts’ interpretations vary with agendas: advocacy groups stress root causes and asylum access, while security‑focused committees highlight nationalities on watchlists and breadth of origins; readers should note these perspectives when judging which countries are emphasized in any particular report ^{[9] [10]}.

6. Bottom line

Based on CBP reporting and the contemporaneous analyses available, the largest shares of undocumented migrants apprehended at the U.S. southern border in 2025 came first from Mexico as a single country, and then from the Northern Triangle countries—El Salvador, Guatemala and Honduras—while South American, Caribbean and other non‑contiguous countries accounted for a growing slice of the total; precise, audited country‑by‑country percentage shares for all of FY2025 are not provided in the supplied sources, so this conclusion synthesizes reported totals and multiple analysts’ summaries rather than reproducing an unavailable official breakdown ^{[1] [2] [3] [4] [7]}.