The objective of the present study was to compare short and long term application of Echinacea purpurea root powder on growth performance and immunity response of broiler chicks. Three replicate trials involving a total of 600 day-old Ross chicks were used in this study. In each trial, a total of 200 chicks were randomly allocated into 5 groups. Each group consisted of 4 pens with 10 chicks in each pen. The birds in group A received control mash diet during the experiment, but those in groups B and C were given control diet supplemented with 0.1% (w/w) and 0.5% (w/w) E. purpurea root powder, respectively. The chicks in groups D and E received control diet supplemented with 0.1% (w/w) and 0.5% (w/w) E. purpurea root powder, respectively, just for one week and fed control diet afterwards. The results showed that E. purpurea consumption for six weeks changed the total counts of white blood cells (WBCs), number of lymphocytes and heterophils, feed conversation ratio, and antibody titers against newcastle and avian influenza diseases (p < 0.05). In conclusion, this result suggests that feeding E. purpurea, particularly for long time, may improve feed conversion, change blood cells number and enhance immunity response in broilers.