Eccard was born at Mühlhausen, in present-day Thuringia, Germany. At the age of eighteen he went to Munich, where he became the pupil of Orlando Lasso. In his company, Eccard is said to have visited Paris, but in 1574, he was again at Mühlhausen, where he resided for four years. There he, together with Joachim a Burck, edited his first master, a collection of sacred songs, called Crepundia sacra Helmboldi (1577). Soon afterwards he obtained an appointment as musician in the house of Jacob Fugger, the Augsburgbanker.
Eccard's works consist exclusively of vocal compositions, such as songs, sacred cantatas and chorales for four or five, and sometimes for seven, eight, or even nine voices. Their polyphonic structure is a marvel of art and still garners the admiration of musicians. At the same time his works are instinct with a spirit of true religious feeling. His setting of Martin Luther's words Ein feste Burg ist unser Gott (A Mighty Fortress Is Our God) is still regarded by the Germans as their representative national hymn.