The traditional cucumber sandwich is composed of paper-thin slices of cucumber placed between two thin slices of crustless, lightly buttered white (or wheat in some cases) bread. As the thinness of the bread is a point of pride in the kitchen, a dense-textured white Pullman loaf is cut with a wide-bladed knife, which guides the cut; daylight should pass through the resulting fine pores. The peel of the cucumber is either removed or scored lengthwise with a fork before the cucumber is sliced. The slices of bread are carefully buttered all the way to the edges in the thinnest coating, which is only to prevent the bread from becoming damp with cucumber juice, and the slices of cucumber, which have been dashed with salt and lemon juice, are placed in the sandwich just before serving in order to prevent the sandwich from becoming damp enough to moisten the eater's fingers. The crusts of the bread are cut away cleanly, creating tea sandwiches.

The traditional cucumber sandwich is of British origin. Modern variants (largely of American origin) exist, involving cream cheese, chopped dill or spices, brown bread, salmon, and even bread with crusts left intact. One specific American variant includes benedictine, a green soft spread based on cucumbers and cream cheese. Cucumber sandwiches are most often served for a light snack or at afternoon tea, a formal light meal served at four in the afternoon or early evening before the main supper. In addition, cucumber sandwiches can be served in the tea break at club cricket matches in England. Because of English influence on Indian culture, cucumber sandwiches are popular during cricket matches and weekend picnics. The Indian variant is flavoured with green chutney and sometimes contains slices of boiled potatoes. Because of cucumber's cooling nature, cucumber sandwiches are often eaten in the summer months or in warmer climates, such as in parts of India.