Serrano, D-N.Y., issued a statement announcing he is living with Parkinson's and although he initially planned to continue his work in the U.S. House of Representatives after his diagnosis, he will retire next year.
"Although this disease has not affected my work in Congress, over the last few months I've come to the realization that Parkinson's will eventually take a toll, and that I cannot predict its rate of advancement. Because of this uncertainty, I do not intend to seek re-election in 2020. I do intend to serve the remainder of my term in the 116th Congress," he said.
Serrano, 75, is the most senior Hispanic Democrat in Congress, as well as the longest-serving Puerto Rican in Congress, having served in the House since 1990.
In addition to representing New York's 15th Congressional District, Serrano is a senior member of the exclusive House Committee on Appropriations and serves as chairman of the Subcommittee on Commerce, Justice and Science.
"As I start to take stock of my career, I am extremely proud of the work we did to revitalize the Bronx River, to bring billions of federal dollars to our borough, to expand access to the ballot for language minorities, to increase STEM resources for minority students, to end the bombing of Vieques, to make our immigration policies fairer and our foreign policies better, to provide legal services for the poor, and to push for a fair and accurate Census," Serrano said.
Serrano added that he will use his final days in office to continue fighting for climate change research, a fairer justice system and an accurate 2020 Census count.
"I pledge to my constituents that I will be here fighting for you until my last day in office and beyond. I am grateful to all my colleagues for their dedication to our community, and for the years we spent working together on so many important issues," he said.