John Holbrook and Kit Tyler of The Witch of Blackbird Pond both travel to Wethersfield on the Dolphin. John is about the same age as Kit, and he is a Puritan interested in making a life for himself as a reverend. He is an intellectual, but he has had to study on his own, being unable to afford the fees to become formally educated. John's attachment to the Reverend Dr. Bulkeley holds him back from developing his personality and his own direction in life, and it is not until he separates himself from the reverend that he can become his own person. This struggle to be his own person manifests in the decisions John must make around his own marriage; though he loves Kit's cousin Mercy Wood, it is Mercy's strong-minded sister, Judith, who pursues John. By the end of the novel, John is able to stand on his own proverbial two feet and marry the woman he loves, proving he can actually be an independent person.

John Holbrook first meets Kit aboard the ship, the Dolphin, on their way to Wethersfield. His plan is to study theology and medicine under the well-known Reverend Gershom Bulkely. Eventually he would like to serve a small parish of his own. John is a gentle soul and an important character in “The Witch of Blackbird Pond.” The arrival of John and Kit changes the relationship dynamics of several young people (Judith, Mercy and William). As the story progresses, John finds the strength to speak up for himself and stand up for what he believes.

John Holbrook is a reverend-in-training. He "has come to Wethersfield to study theology with the Reverend Dr. Gersholm Bulkeley, a real historical personage." He is probably in his late teens.