Ectoparasitic arthropods represent a significant component of faunal biodiversity, with high zoological and veterinary relevance due to their parasitic adaptations and role as vectors of pathogens. This study provides a detailed morphological and biological characterization of four ectoparasitic taxa identified in domestic mammals examined at the “Medicrisvet” Veterinary Clinic (Fălticeni, Suceava, Romania) during 2024: Otodectes cynotis, Rhipicephalus sanguineus, Demodex cati, and Demodex criceti. Specimens were collected from dogs, cats, and hamsters and examined using optical microscopy to document diagnostic morphological traits, developmental stages, and host specificity, with careful attention to subtle variations in body structure, appendages, and cuticular patterns. Quantitative analysis of infestation data revealed Rhipicephalus sanguineus as the dominant species (43% prevalence), followed by O. cynotis (29%), D. cati (18%), and D. criceti (10%), highlighting differences in host preference, seasonal distribution, and potential risk of transmission. The observed morphological variability highlights adaptive features related to host microhabitat, feeding behavior, and environmental interactions. This work contributes new faunistic and morphological data on ectoparasitic arthropods from northeastern Romania and supports their taxonomic documentation within the broader context of veterinary and systematic zoology. The findings emphasize the integrative role of detailed morphological analysis in understanding host–parasite associations, local prevalence patterns, and the regional biodiversity of parasitic arthropods, ultimately providing a basis for improved monitoring and control strategies in domestic animal populations.