The most frequent cause of hammer toe is a muscular and/or tendinous imbalance. This imbalance is due to mechanical (structural) changes in the foot. Non-surgical solutions can relieve pain but will not directly treat the cause of deformity.

Hammer toes often get worse due to unsuitable footware, for example shoes that squash the toes. In certain cases, ill-fitting shoes can be the cause of the joint deformity responsible for the onset of hammer toes. For example, a hammer toe can develop if the toe is too long and is bent in a shoe that is too narrow.

Hammer toes can be hereditary or caused by trauma, such as following a fracture.