Alexander Dinelaris Jr. is a screenwriter. He is one of four who won the Academy Award for Best Original Screenplay for the 2014 film Birdman at the 87th Academy Awards in 2015. Dinelaris also wrote the book for the Broadway musical On Your Feet, which is about the life and career of Gloria Estefan. For this, he was nominated for the Outer Critics Circle Award for Outstanding Book of a Musical. In 2019, he formed his New York-based production company, Lexicon. He announced that its first feature film will be an adaptation of the Broadway musical Jekyll & Hyde, which Dinelaris will adapt into a screenplay and produce. That same year, he filmed the short film In This, Our Time, which he wrote and directed.

Alexander Dinelaris Jr conducted the first workshop of Boman Irani's Spiral Bound. On February 8, 2023, it was announced that Alexander Dinelaris Jr is working with Residente to co-write a new film, Porto Rico.