We determined hematologic parameters of five healthy and nine sick free-ranging Lesser Flamingos (Phoeniconaias minor) from Lake Nakuru, Kenya. Heterophilia and lymphopenia were evident in sick birds, with up to 7.5-fold higher heterophil-to-lymphocyte ratio in sick birds compared to healthy birds. Leucopenia was present in a few sick birds. A higher than normal packed cell volume was observed in birds that had evidence of acute disease, whereas a lower than normal packed cell volume was seen in birds with evidence of prolonged sickness. Healthy birds had higher total white blood cell counts and lymphocyte counts and lower heterophil counts than zoo flamingos. Most sick birds were diagnosed with septicemia, occasionally with fibrinous exudation into the coelomic cavities. One bird had mycobacterial granulomas, one had a corynebacteriumassociated wing abscess, and one had a wing fracture. We provide hematologic data for freeranging Lesser Flamingos and compare the parameters of sick and healthy birds.