A cap sleeve is a specific sleeve style found on short sleeve shirts, dresses, and other garments. In fashion, "cap sleeve" is generally a descriptor reserved for women’s blouses and T-shirts, though it refers more to the specific cut or style of garment, indicating that the sleeve is cut and seamed to fit the shoulders correctly. A cap sleeve shirt is usually not as loose about the upper arms as the standard men’s T-shirt. The length of a cap sleeve is also slightly shorter than a standard short-sleeved shirt with the average length being between 1.5 inches (3.8 cm) to about 4 inches (10.2 cm).

Cap sleeve shirts can be casual or formal, such as those worn under a suit blazer. Cap sleeve dresses can also be casual or formal. However, a cap sleeve garment is always short sleeved. A number of shirt styles for women are described as cap sleeve shirts, including T-shirts. Cap sleeve T-shirts are particularly popular amongst young girls and women, especially when the shirt is cut to fit the waistline as well. This style of shirt is generally sold with the descriptor “cap sleeve tee.”

Cap sleeve blouses are simply a style of short sleeve blouse that fits well under a blazer or jacket because the sleeves are cut to fit and do not bunch up around the upper arm and armpit area. Similarly, a cap sleeve dress can be coupled with a blazer, jacket, or sweater and be comfortable to wear as well. Though a cap sleeve blouse may have a collar, most cap sleeve shirts are collarless with varying neckline styles.

Cap sleeve shirts are available in an assortment of materials from cotton to rayon to stretch knit. Both high-end designers and mass retail labels use the descriptor “cap sleeve” to describe a wide assortment of women’s tops and dresses. They are considered a more feminine version of the standard T-shirt and are available in an array of patterns and styles.