A study on bovine babesiosis and its vector was conducted at Kobo and Girana valleys of North Wollo Zone in Amhara National Regional state, Northern Ethiopia. The objective of the study was to determine the prevalence and identify at species level of bovine babesiosis and the vector and indicate the associating risk factor for Boophilus decoloratus tick through longitudinal study. A total of 370 cattle from both valleys were used for a cross sectional study while 60 cattle were also involved in longitudinal study during four consecutive seasons. The longitudinal study was conducted on October, December, January and March that represents late rain, early dry, late dry and early rain seasons respectively. The prevalence of Babesia bigemina in a cross sectional study of age groups 4) was (20.3%, 24.3%, and 16.1%), respectively. The prevalence of B. bigemina among the three age groups was not statistically (p>0.05) significant. Sex (male and female) basis of Babesia bigemina infection rate were (12.7% and 7.6%) respectively and high infection rate (26.5%) were observed in animals with poor body condition than animals with good body condition (15.19%). The prevalence of sex and body condition wise was found statistically (p0.05) significant. The infestation rate of Boophilus decoloratus in age groups (4) were 73.2%, 82.1% and 91.9%), respectively. And sex (male and female) wise infestation rate were (86.6% and 78.3%), respectively. Age and sex wise prevalence was found statistically (p