To determine prevalence and diversity of Eimeria species in commercial turkey flocks, fecal samples (n=39) representing 27 commercial turkey farms (ON-20, SK-2, BC-3, AB-1, NS-1) were screened for coccidia; parasite diversity was determined using nested polymerase chain reactions targeting mitochondrial cytochrome c oxidase subunit I. Most samples (34/39) were Eimeria-positive with 1 to 6 species present (average 3.2 species/sample). An in vivo trial evaluated potential immunological cross-protection among the 6 detected Eimeria species. Protection against lesion development and reduced weight gains, and parasite fecundity were measured following high and low dose challenges, respectively. Significant adaptive immunological protection against lesion development, growth reduction, and parasite replication (95.4-100% reduced oocyst output) was demonstrated following homologous challenges. No adaptive immunological cross-protection between Eimeria species was detected. Diverse Eimeria species were both plentiful and widespread in Canadian commercial turkeys; the data reported herein will assist in the management of coccidiosis in commercial turkey operations.