Inflammatory colorectal polyps (ICRP), which are more commonly recognized in miniature dachshunds, are thought to represent an immune-mediated disease. This retrospective case series describes six miniature dachshunds with refractory ICRP, who were treated with chlorambucil (CLB) combined with firocoxib or prednisolone. Improvement in clinical manifestations was seen in five of the six dogs by the end of the study period; four were treated with CLB/firocoxib and one with CLB/prednisolone. One dog had nonregenerative anemia after 23 mo of treatment with CLB, but whether there was a causative relationship was unclear. No severe adverse events were observed during treatment in the remaining five dogs. CLB in combination with firocoxib or prednisolone appears to be an effective alternative treatment for ICRP in dogs. Further studies are needed to confirm the effectiveness and long-term complications of CLB treatment for ICRP in dogs.