After his return to the island in 1880, Barbosa made many contributions to medicine and public health. He initiated an early form of health insurance, encouraging employers to pay a fee to cover future needs of their employees. In 1900 Barbosa was among the first five Puerto Rican leaders appointed to the Executive Cabinet under Governor Charles H. Allen, in the first civilian government organized by the United States. He served in the Cabinet until 1917. From 1917–1921, Barbosa served in the first elected Puerto Rican Senate.