Haematological parameters, plasma iron concentration, and bodyweight were monitored in Melanoma-bearing Libechov Minipigs (MeLiM) from 5 to 18 weeks old. Animals with melanoma progression (P group) and spontaneous regression (SR group) were compared. The P group showed the lowest median values of red blood cell counts (RBC), haematocrit (HCT), haemoglobin concentration (HGB), and bodyweight, whereas the control white (tumour-free) pigs (C group) revealed the highest mean values of these parameters. The mean values of pigs with SR fell between the P and C groups. In addition, a stable concentration of plasma iron was found in the C group, while iron deficiency that increases with age was observed in the MeLiM groups. These results indicate that MeLiM are affected by cancer-related microcytic hypochromic anaemia. The lowest values of HGB, RBC, and HCT, together with the highest number of platelets (PLT) in the P group correspond to melanoma progression. Higher values of these parameters and lower PLT in the MeLiM pigs with SR reflected health improvement due to the destruction of melanoma cells during spontaneous regression. Monitoring of these haematological parameters can help distinguish MeLiM piglets with progression and spontaneous regression of melanoma in the early stages of postnatal development. The findings of this study correspond to findings in human patients in which cancer-related anaemia, thrombocytosis, and iron deficiency are often diagnosed.