Domains have been observed in TbxHo1−xFe1.9 over the composition range 0<x<0.2 and temperature range −10 to +100 °C, as a function of bias field. In the region where this system is 〈100〉 easy, the movement of {110} 90° domain walls is shown to be responsible for the generation of negative magnetostrain, with increasing bias field. When 〈111〉 is easy, 71° domain walls in {110} have been identified with a bias field applied. For x=0.1, at remanence, 180° domain walls rotate smoothly with increasing temperature, from {100} when 〈100〉 is easy to {110} when 〈111〉 is easy. The presence of a bias field, at any temperature, brings out {110} walls which are 90° walls in the 〈100〉 easy, low temperature, regime and 71° walls in the 〈111〉 easy, high temperature, regime. At intermediate temperatures these walls remain in {110} with the magnetization in directions between 〈100〉 and 〈111〉. These domain observations are shown to be consistent with theoretical magnetomechanical behavior based on a 〈1uu〉, 0<u<1, transition in easy axis.