John Pendleton, a wealthy and reclusive resident of Beldingsville, lives alone in a large, cluttered mansion without servants. He initially presents a cold, unsociable exterior, shunning greetings and interactions with townspeople, fueling rumors about his solitary life and a possible "skeleton in his closet."

His past reveals a deep love for Jennie Harrington, Pollyanna's mother. After Jennie chose to marry Reverend John Whittier, Pendleton became embittered and withdrawn, carrying unresolved grief for decades. This rejection fundamentally shaped his isolated existence.

His interactions with Pollyanna spark significant change. After sustaining a leg injury in the woods, Pendleton is aided by Pollyanna, who fetches medical help. During his recovery, she visits him regularly, engaging him in conversations about finding joy in small things, like rainbows created by sunlight through prisms. Her presence and resemblance to Jennie initially stir painful memories but gradually soften his embittered heart.

As their bond deepens, Pendleton reveals his past with Jennie to Pollyanna, confessing her optimism has reawakened his capacity for connection. He eventually asks to adopt Pollyanna, hoping to fill his lonely life with familial warmth. Though touched, Pollyanna declines, choosing to remain with her Aunt Polly. This second rejection prompts Pendleton to redirect his paternal instincts, adopting the orphan Jimmy Bean instead.

Following Pollyanna’s accident, Pendleton visits her bedside, applying the "Glad Game" philosophy she taught him to help her cope with her paralysis. His transformation culminates in active community reintegration, demonstrated by his care for Jimmy and participation in Pollyanna’s recovery celebrations.