Brave New World is not typically seen as a work of transcendentalism. However, it could arguably be seen in that way because it depicts Huxley’s view of what happens if a society moves too far away from some of the tenets of transcendentalism.
Transcendentalism is a very individualistic philosophy. It is known for ideas such as Ralph Waldo Emerson’s idea that anyone “who would be a man must be a nonconformist.” It is known for Henry David Thoreau’s idea that most people “lead lives of quiet desperation” because they are stifled by the need to conform.
We can understand Brave New World as a warning about what happens when conformity is allowed to dominate and people’s own emotions are stifled. We can see how Bernard Marx is struggling with the tension between his desire to be an individual and his desire to fit in to society. We can see the same with Helmholtz Watson. In the case of John the Savage, we can see what happens when a person who has not been indoctrinated into conformity is suddenly forced into a society that prizes that trait.
In these ways, we can say that Brave New World is related to transcendentalism because it depicts life in a society in which transcendentalist values are largely absent.