Piñero was born on December 19, 1946 in Gurabo, Puerto Rico to Miguel Angel Gomez Ramos and Adelina Piñero. In 1950, when Miguel was four, he moved with his parents and sister Elizabeth to Loisaida (or Lower East Side) in New York. His father abandoned the family in 1954 when his mother was pregnant with their fifth child. His mother then moved into a basement and began receiving welfare. He attended four different schools, three public and one parochial. He would steal food for his family to eat. His first of what would be many criminal convictions was at the age of eleven for theft. He was sent to the Juvenile Detention Center in the Bronx and also to Otisville State Training School for Boys. He joined a street gang called "The Dragons" when he was 13, and when he was 14 he was hustling in the streets.
He would move to Brooklyn, where he and three other friends would commit robberies (according to Piñero, they did over 100), until they were caught at a jewelry store. He would be sent to Rikers Island in 1964. After this, he joined the Job Corps and was sent to Camp Kilmer for training. It turned out the opportunity was, as Piñero put it, "Dope City, Skag Town." He returned to New York City and became affiliated with the Young Lords, similar to the Black Panthers. He was back in Rikers for drug possession not long after, and even went to Phoenix House. After his second stint at Rikers, his mother sent him to Manhattan State Hospital where he would receive his high-school equivalency diploma.
In 1972, when Piñero was 25 years old, he was incarcerated in Sing Sing prison for second-degree armed robbery. His first literary work was Black Woman with a Blonde Wig On. Marvin Felix Camillo, the director of The Family, an acting troupe made up of ex-cons, submitted the poem to a contest, which it won. The warden of Sing Sing then became concerned that "contraband" was being taken from the prison and nearly put Camillo in jail after seeing an article in the newspaper. While serving time in prison, he wrote the play Short Eyes as part of the inmates playwriting workshop. Mel Gussow came to see it, and due to his review in the New York Times, the director of the Theater at Riverside Church wanted Piñero to put it up at his place.
When he left Sing Sing due to parole in 1973, he was able to put Short Eyes with The Family. The title comes from the slang for pornography "short heist", but since the Puerto Ricans could not pronounce the 'h' so it became short eyes. The play is a drama based on his experiences in prison and portrays life, love and death among prison inmates. In 1974, the play was presented at Riverside Church in Manhattan. Theater impresario Joseph Papp saw the play and was so impressed that he moved the production to Broadway. It went from Riverside Church, then to The Public Theater, eventually to Vivian Beaumont Theatre. The play was nominated for six Tony Awards. It won the New York Drama Critics Circle Award and an Obie Award for the "best play of the year". The play was also a success in Europe. It catapulted Piñero to literary fame. Short Eyes was published in book form by the editorial house Hill & Wang. It became the first play written by a Puerto Rican to be put on Broadway.
In the 1970s, Piñero co-founded the Nuyorican Poets Café ("New York-Puerto Rican") with a group of artists, one of which, Miguel Algarín, would become one of his best friends. The Cafe is a place for performance of poetry about the experience of being a Puerto Rican in New York.
In 1977, Piñero's play "Short Eyes" was turned into a film directed by Robert M. Young. In the film Piñero played the part of "Go-Go", a prisoner. While on set, he and Tito Goya were arrested for armed robbery and were arraigned in the same building where they were filming. The charges were dropped, but some people thought Piñero had a "need" to go back to prison. He would land some supporting roles The Jericho Mile (1978), Times Square (1980), Fort Apache, The Bronx (1981), Breathless (1983), Deal of the Century (1983), and Alphabet City (1984). Piñero was considered a talented writer who described the evils of society, even though he continued to be a drug addict. Piñero wrote the Baretta TV episode The Gadjo in 1978 and acted in the episode Por Nada in 1977. He wrote the Miami Vice TV episode "Smuggler's Blues" in 1984 and the screenplay for Short Eyes (the movie).
His next play, Sideshow (1974), which would be a shorter version of Playland Blues (1980), and follows street kids as they decide to put on their own play about a social worker placing difficult teenagers in various living situations and their attempts to adapt.
His next play, a one act titled The Guntower, premiered at the 1976 New York Shakespeare Festival. Instead of following prisoners, like in Short Eyes, this one is about two guards in the watchtower. In that same year was The Sun Always Shines for the Cool (1976) which follows the lives of players, operators, drug dealers, and thieves as they come together in a bar owned by a man named Justice.
In 1975, he moved to Philadelphia to star in Bruce Jay Friedman's Steambath as God. Eulogy for a Small-Time Thief (1977) was set in his new hometown. It regards a small time thief who does not really know his place in the world and thinks he can manipulate it to his liking.
He wrote two one-act plays, Paper Toilet and Cold Beer, around 1979. The former is set in a subway men's room and involves a series of events framed by the voice of a man asking for toilet paper from inside a stall. The latter examines the role of the dramatist and writer through an alter-ego protagonist.
Piñero played an important role in acquainting partner, artist Martin Wong with the Lower East Side, becoming a benefactor at a time when Wong found it difficult to meet his rent. Several of Wong's paintings are illustrations of poems given to him by Piñero. "The Annunciation According to Mikey Piñero (Cupcake and Paco)" (1984) pictures a scene from Short Eyes.
Miguel Piñero died on 16 June 1988 in New York City from cirrhosis. Piñero's ashes were scattered across the Lower East Side of Manhattan, as he asked in his 1985 "Lower East Side Poem." The homage to his beloved neighborhood concluded:
Leading up to his death, he was working with Papp for a new play to premiere at the New York Shakespeare Festival. Every Form of Refuge Has Its Price his unfinished piece, is set in an intensive-care unit. He also had another unfinished play, The Cinderella Ballroom.
Typescripts for Miguel Piñero's The Guntower and All Junkies are in the Billy Rose Theatre Collection at the New York Public Library for the Performing Arts.
The life of Miguel Piñero was portrayed in the Hollywood production Piñero, directed by Leon Ichaso and starring Benjamin Bratt as Piñero. In the film, Piñero's love life is displayed, ranging from his interactions with men and women, including his protégé Reinaldo Povod. The relationships are secondary to the life of the writer as an individual, as the movie shows a non-chronological portrayal of Piñero's development as both a poet and a person. The movie blends visual and audio segments shot in short, music/slam poet videos with typical movie narratives to show Piñero's poetics in action.