In this study, flow around an in-line array of spheres has been investigated, focusing on the interaction between the sphere wakes. In a circulating water tunnel, 12.7 mm-diameter steel balls have been aligned along the direction of flow, with each sphere held by a thin steel wire. Considered Reynolds number for a single sphere is 1,000 and the number of spheres is increased up to five with varying the distance between them, as well. PIV and dye visualization has been used in order to measure the velocity fields and vortex shedding frequency. It is found that hairpin vortices are periodically detached from each sphere, move to downstream and undergo active interaction with other sphere’s wake. For the case of an array with two spheres, three distinctive flow structures have been identified depending on the distance between spheres. When the number of the spheres added, we find that there exists a specific trend on the Strouhal number. Also, the time-averaged velocity field and turbulence intensity in the wake will be discussed depending on the considered conditions.