A xenogeneic DNA vaccination has been licensed for use in dogs with locally controlled stage II and III oral malignant melanoma (OMM). At present, there are limited outcome data for dogs with OMM treated with surgery and immunotherapy. The aim of this study is to retrospectively review the outcome and survival of 32 dogs affected by OMM that were treated with a combination of surgery and the xenogeneic DNA vaccination (with the addition of radiotherapy in some cases) and to determine the influence of surgical margins and delay in receiving vaccination. The overall median survival time (MST) was 335 days (95% CI: 301–540 days), and the overall median progression-free survival (PFS) was 160 days (mean 182 days, 95% CI: 132–232 days). Stage, completeness of surgical margins and delay in administration of the vaccine did not appear to statistically influence survival or PFS, although these results may reflect the low statistical power of the study due to small numbers. Further studies are required to assess whether the addition of any adjuvant treatment to surgery, including immunotherapy, is able to significantly prolong survival in cases of canine oral melanoma.