The exact year of the painting's completion is unknown, with estimates varying by source.

Despite its traditional title, the picture clearly shows a kitchen or housemaid, a low-ranking indoor servant, rather than a milkmaid who actually milks the cow, in a plain room carefully pouring milk into a squat earthenware container on a table. Also on the table are various types of bread. She is a young, sturdily built woman wearing a crisp linen cap, a blue apron and work sleeves pushed up from thick forearms. A foot warmer is on the floor behind her, near Delft wall tiles depicting Cupid (to the viewer's left) and a figure with a pole (to the right). Intense light streams from the window on the left side of the canvas.

The painting is strikingly illusionistic, conveying not just details but a sense of the weight of the woman and the table. Yet with half of the woman's face in shadow, it is "impossible to tell whether her downcast eyes and pursed lips express wistfulness or concentration," she wrote.

"It's a little bit of a Mona Lisa effect" in modern viewers' reactions to the painting, according to Walter Liedtke, curator of the department of European paintings at The Metropolitan Museum of Art, and organizer of two Vermeer exhibits. "There's a bit of mystery about her for modern audiences. She is going about her daily task, faintly smiling. And our reaction is 'What is she thinking?'"