Carthy-Deu was born in San Juan, Puerto Rico to Ramón Carthy Sanchez and Vicky Sanz Deu, of Irish and of Puerto Rican descent. Her mother directed Academia de Ballet y Modelaje Vicky Sanz, an academy for ballet and modeling, under the name of Vicky Sanz. Her father was a photography director.
Carthy-Deu attended Commonwealth High School located in San Juan, Puerto Rico. Afterwards, she attended the University of Puerto Rico where she graduated Manga Cum Laude with a degree in theater arts and education. She was awarded the Theater Medal, which was given to the most distinguished graduate of the class.
While attending college, Carthy-Deu won the title of Miss San Juan 1985 on March 22, 1985. She advanced to the Miss Puerto Rico Pageant later that year where she was crowned Miss Puerto Rico 1985 on April 27, 1985.
After winning the Miss Puerto Rico crown, Carthy-Deu represented her country at the 34th annual Miss Universe Pageant. She was crowned Miss Universe 1985 on July 15, 1985, at the James L. Knight Convention Center located in Miami, Florida.
Since passing on her crown, Carthy-Deu has had a successful career in television and film. Immediately after crowning her successor, she traveled to Argentina to portray the leading character in the telenovela, “El Cisne Blanco.”
In addition, Carthy-Deu has hosted several television shows in Puerto Rico, New York City and Miami. In connection with Univision and the Telemundo, she has worked on “Noche de Gala,” "Desde Mi Pueblo" and "La Buena Vida.”
Along with her television work, Carthy-Deu has wrote a column for The San Juan Star, been a fashion contributor for WAPA's newscast "Noticentro Al Amanecer" and maintained a fashion review at the now closed publication “Teve Guia”
Currently, Carthy-Deu owns a modeling and finishing school, known as Deborah Carthy Deu Estudio y Agencia de Modelos. Her mission is to help girls and women develop social skills, self-esteem and start careers in modeling, the arts, television and pageants.