Tree bumblebees have distinctive markings that distinguish them from other bumblebees. They have a black head and a thorax that is reddish-brown to tawny. The abdomen is usually black with a white tail, occasionally the gingery thorax colour will spread to the abdomen but there is always a strip of black before the white tail. There can also be dark forms of tree bumblebees but they still have the white tail and are fluffier than similar coloured bumblebees.
Unlike other bumblebees, tree bumblebees can wear a bald patch in the gingery hair of the thorax.
The size varies between 10 – 16mm, with the largest bees are queens and the smallest are workers.