The Marsh Tit is less scruffy looking than the Willow Tit and has a neater, smaller bib and glossier black cap. Also, the Marsh Tit lacks the pale wing panel, does not look "bull-necked" and usually has a square-ended tail but is sometimes slightly forked. A more reliable method of differentiating the two species is by their calls. The Marsh Tit call sounds like a ringing sneeze, "pitchoo", which sometimes precedes a trilling "chickabeebeebeebee".

Marsh Tits feed on insects and seeds, such as beech mast. Peanuts, seeds and fat may attract them to gardens, but usually only if there are ancient woodlands nearby (contrary to their name, they do not live in marsh land). They are particularly fond of black sunflower seeds.

The female builds the nest, which is a cup of moss lined with feathers and hair, in a hole in a tree. They usually nest in deciduous trees, like willows or alders, but will sometimes use a box. The Marsh Tit's eggs are smooth and glossy, and white with brown markings. The female incubates the eggs by herself. After the young hatch, they are fed by both parents. The Marsh Tit is a Red List species owing to a large, rapid decline in the breeding population since the 1960s, most likely because of changes in land usage and woodland management.