B. officinalis grows to a height of 60 centimetres (2 feet), and is bristly or hairy all over the stems and leaves; the leaves are alternate, simple, and 5–15 cm (2–6 inches) long.

The flowers are complete, perfect with five narrow, triangular-pointed petals. Flowers are most often blue, although pink flowers are sometimes observed. White-flowered types are also cultivated. The blue flower is genetically dominant over the white flower.

The flowers arise along scorpioid cymes to form large floral displays with multiple flowers blooming simultaneously, suggesting that borage has a high degree of geitonogamy (intraplant pollination).

It has an indeterminate growth habit. In temperate climates such as in the UK, its flowering season is relatively long, from June to September. In milder climates, borage blooms continuously for most of the year. It can be invasive.