Few studies have examined platelet alterations in dogs with chronic enteropathy. Our aim was to investigate platelet count (PLT), mean platelet volume (MPV), and platelet-tolymphocyte ratio (PLR) in dogs diagnosed with immunosuppressant-responsive enteropathy (IRE). In this retrospective study of 41 dogs, data regarding signalment, canine chronic enteropathy clinical activity index (CCECAI), endoscopic and histopathological scores, PLT, MPV, PLR, total serum protein concentrations, albumin, and iron were collected. Clinical response and relapse were assessed with the evaluation of CCECAI over time. One month after starting therapy, dogs with >25% CCECAI reduction were considered responders. During a three-month CCECAI evaluation as part of a twelve-month follow-up, a CCECAI >3 together with a ≥2 unit increase in responder dogs was considered a relapse. PLT and PLR displayed significant negative correlation with MPV. MPV was positively correlated with total protein and albumin levels and negatively correlated with CCECAI. Three dogs were classified as non-responders, and 14 relapsed within 12 months. No differences were observed in PLT, MPV, or PLR between responding/non-responding and relapsing/non-relapsing groups. PLT, MPV, and PLR correlated with total protein, albumin, and CCECAI, confirming PLT as a potential marker, and suggesting MPV as a new marker of clinical efficacy against canine IRE.