In 1978, he abandoned his freelance career to spend 18 months as a principal of the New York City Ballet, run by the legendary George Balanchine. "Mr. B," as Balanchine was known, rarely welcomed guest artists and had refused to work with both Nureyev and Makarova. Baryshnikov's decision to devote his full attentions to the New York company stunned the dance world. Balanchine never created a new work for Baryshnikov, though he did coach the young dancer in his distinctive style, and Baryshnikov triumphed in such signature roles as Apollo, The Prodigal Son, and Rubies. Jerome Robbins did, however, create Opus 19/The Dreamer for Baryshnikov and NYCB favorite Patricia McBride.
Baryshnikov performed with the New York City Ballet as a principal dancer for 15 months from 1978 to 1979. On July 8, 1978, he made his debut with George Balanchine's and Lincoln Kirstein's company at Saratoga Springs, appearing as Franz in Coppélia.