[6][7] Nothing is known about his teachers but it is assumed that he may have been apprenticed either to Hans Hirtz of Strasbourg or Konrad Witz of Basel; his art also shows the influence of Rogier van der Weyden and his school.

[6] After 1450, Isenmann is registered as an alderman (Schöffe) and in 1461, he is one of the main organizers of a Mystery play during Corpus Christi.

[6] In 1462, Isenmann received a commission to paint a set of panels (oil on fir wood) for the high altar of St Martin's Church, Colmar's main place of worship, and he delivered the finished altarpiece in 1465.

[8] It was signed on 21 June 1462; the painter was guaranteed a payment of 500 guilder and requested to complete work in two years, i. e. in 1464.

Between 1466 and 1469, Isenmann may have been the teacher of fellow Colmarian, Martin Schongauer, whom he acquainted with van der Weyden's paintings.