In Portrait of Harpje, Aged 15, we see a young girl with delicate features and a serene expression. The artist uses soft colors, primarily pastels, to create a gentle atmosphere. Harpje is dressed in a simple yet elegant outfit, which highlights her youth.

The background is muted, allowing the viewer to focus on her face and attire. This painting is executed in oil on canvas, a common medium for portraits during the Dutch Golden Age. The brushwork is smooth, contributing to the lifelike quality of Harpje's skin and hair. The composition is balanced, with Harpje positioned slightly off-center, drawing the viewer's eye.

The use of light and shadow adds depth to the painting. Richard Nicolaüs Roland Holst was known for his portraits and depictions of youth. This particular work, painted around the early 1900s, reflects the artist's interest in capturing the innocence of childhood. An interesting fact about this painting is that it was created during a time when portraiture was evolving, moving towards more intimate and personal representations.