Competent in drawing since childhood, Abreu made his first drawings aged 9 and 10, when he painted his first landscapes, and moved to Caracas at a young age. He worked as a laborer in Casa Benzo while studying at night to finish his primary education. Later he attended night school from 9 to 11 pm at the Caracas School of Fine and Applied Arts, directed by Antonio Monsantos. In 1942, after winning a painting competition and winning a scholarship worth 100 bolivars per month, he was able to leave work and attend the day courses at the same school, from which he graduated in 1947. He participated in the Free Art Workshop, founded the year after his graduation.
In 1951, Mario Abreu received the National Prize for Painting at the XII Annual Official Hall Venezuelan Art, allowing him to get a scholarship to continue studies in Europe. Between 1952 and 1961 he lived in Paris, where he developed an intense intellectual life and began a new phase of his work.
He returned to Caracas in 1961.
In 1967 he exhibited in the São Paulo Biennale.[4][3]