During the Obama Administration, Aguilar supported expanding the Deferred Action for Childhood Arrivals (DACA) program for undocumented children and creating the Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA) program. Aguilar introduced the Academic Success Centers and Education Networks for Dreamers (ASCEND) Act, which would establish grants for college and university programs and services to benefit undocumented students. While Aguilar voted in favor of legislation that would effectively halt the resettlement of refugees from Syria and Iraq to the United States, citing national security concerns, he subsequently criticized President Donald J. Trump's Executive Order as "xenophobic" and said it sent a message of "hate and bigotry to the rest of the world." Aguilar criticized President Trump and his staff for citing the 2015 San Bernardino attack in defending the President's executive order. In 2018, with Republican Congressman Will Hurd, Aguilar authored legislation that would provide a path to citizenship for DACA recipients and addresses border protection concerns.