The optimal and presumably ancestral habitat of these ticks is forest, although the species is locally abundant in meadows, poorly maintained pastures, and ecotones. Today the tick is even found in parklands of cities and in private gardens.

The adults climb higher in the vegetation and usually only attack large animals from the size of a hare upwards. Hosts include sheep, deer, foxes and hedgehogs; it occurs mainly on sheep and cattle, but occasionally bites also humans.

The life cycle takes up to 3 years to complete, with each life cycle stage (larva, nymph and adult) taking one year - but it can vary in length between 2 and 6 years. I. ricinus is therefore well adapted to the seasonal pattern on the northern hemisphäre.
In most of its geographical range I. ricinus feeds on animals from March to October and 2 sub-populations, one becoming active in spring and early summer and the other smaller one in late summer and autumn, occur in most areas.

The Castor bean tick transmits the pathogen Babesia divergens and B. bovis, which causes Redwater fever. It also transmits Anaplasma marginale, which causes anaplasmosis in cattle and sheep.
It acquired a new significance when in 1983 Burgdorfer et al. identified I. ricinus as a vector of Lyme disease.

Another serious threat in some Ixodid ticks is a nerve poison containing in the tick's saliva that causes paralysis to the host. The so called tick paralysis can also arise from the bite of ticks such as I. ricinus.