Previous work from our lab developed an ultrasound standing wave field (USWF) technology to noninvasively pattern endothelial cells within collagen hydrogels to fabricate vascularized engineered tissue constructs. Here, we translate this technology towards acoustic patterning and microvascular network formation in vivo. To enable acoustic patterning in vivo, we developed a two-transducer ultrasound system with intersecting beams to produce an USWF at the intersection of the crossed beams. Acoustic radiation forces associated with the USWF patterned cells into planar bands located at nodal planes. Distance between planar bands was controlled through design of acoustic frequency and angle between ultrasound beams. To demonstrate acoustic patterning in vivo, solutions of collagen and human umbilical vein endothelial cells (HUVEC) were injected subcutaneously into flanks of mice and then exposed to an USWF. High-frequency ultrasound imaging was employed to visualize initial acoustic patterning in tissues. Ten days after USWF-mediated cell patterning, tissues were excised, and vessels derived from USWF-patterned cells were identified using an antibody specific to human von Willebrand factor (hVWF). Microvessels expressing hVWF were present in USWF-exposed tissues and not in sham-exposed controls. Furthermore, blood vessels expressing hVWF contained red blood cells, indicating anastomosis of ultrasound-fabricated microvessels with host vasculature and tissue perfusion.