Arrarás began serving UPR Chancellor Jaime Benítez as his special assistant in 1962, even before graduating from law school.
As Benítez moved on to become the institution's first system-wide President, Arrarás served as the first chancellor of the University of Puerto Rico's Mayagüez Campus for over 5 years, from 1966 to 1971.
After an unsuccessful run for Mayor of San Juan in 1972 under the Popular Democratic Party banner, Arrarás was appointed in 1973 as the Secretary of the new Housing Department by incoming Gov.
He began his first ten-year stint in the Puerto Rico House of Representatives in 1978, serving as chairman of the powerful Budget and finance committee from 1981 to 1984.
In addition to all that Arrarás accomplished in academia and public office, he has been one of the most prominent figures in organized sports in Puerto Rico for the past four decades.