Sera from 497 sheep and 555 goats collected in a cross sectional study from different geographical locations in north-eastern Tanzania were examined for antibodies to Ehrlichia ruminantium using MAP 1-B ELISA technique. E. ruminantium antibodies were found in 68.6% (341/497) of sheep and 64.7% (359/555) of goats. Overall seroprevalence was 66.5% (700/1052). Infection rates were higher in sheep than goats (P < 0.05), in pastoral than in agro-pastoral production systems (P < 0.05) and in female sheep than males (P < 0.05). (131/143) 91.6% of the farms/flocks tested revealed sero-positive animals. E.ruminantium infections were found in all the geographical villages and districts tested. The infection rates per administrative district varied from 36.4% (Muheza) to 90% (Mkinga) in goats and from 11.9% (Muheza) to 94.6% (Mkinga) in sheep. The results shows E. ruminantium infection was prevalent and widely but unevenly distributed throughout the eight districts under study. These findings should be taken into consideration when future disease control and livestock upgrading programs are implemented.