Haemosporidian parasites, which encompass Haemoproteus, Plasmodium, and Leucocytozoon, are intracellular parasites commonly found in the blood and other tissues of birds worldwide. The prevalence of these parasites can vary depending on the bird species and the habitats they inhabit. Notably, the highest diversity of Haemosporidian parasites has been observed within the Passeriformes order of birds. In our study, we collected 145 blood samples from wild songbirds in the western region of Iran during the period from April to November 2021-2022. Blood smears were prepared using the push-slide method and subsequently stained with Giemsa. The stained smears were then examined under a light microscope, and all samples were screened using a nested PCR protocol that targeted a 479-base-pair segment of the mitochondrial cytochrome b (cytb) gene of Haemoproteus, Plasmodium, and Leucocytozoon species. Among the seven songbird families we sampled, we detected blood parasites in 31 individuals, representing an infection rate of 21.4% (95% CI: 0.1501 to 0.2896). These infected individuals belonged to five different families, and a total of 21 lineages were identified, including thirteen for Leucocytozoon spp, seven for Haemoproteus spp, and one for Plasmodium spp. Notably, the highest infection rates were observed in the Paridae family (9.7%, 95% CI: 0.0537 to 0.1567) and the Motacillidae family (4.8%, 95% CI: 0.0196 to 0.0970), while the lowest infection rates were recorded in the Corvidae family (1.4%, 95% CI: 0.0016 to 0.0490) and the Acrocephalidae family (1.4%, 95% CI: 0.0016 to 0.0490). Additionally, our study documented two new host species for Leucocytozoon spp. (Motacilla flava and Acrocephalus melanopogon), marking the first such observations globally. We also established five new host records (Motacilla flava, Pica pica, Acrocephalus melanopogon, Poecile lugubris, and Acrocephalus agricola) for avian haemosporidian parasites in the western region of Iran. These findings underscore the remarkable lineage diversity within the Leucocytozoon genus compared to other haemosporidian parasites in songbirds in western Iran, setting our study apart from previous research in Iran

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