To achieve high gain and electronic beam steering, phased array systems are commonly used. The phased array technique plays an important role in sensing and communication systems. Practical phased array system usually consists of many components including RF power feeding networks, antennas, and active parts such as phase shifters and amplifiers. Single-layer implementation of phased arrays usually leads to large system size and limited applicability as the functionality becomes more complex. Multilayer structure is useful to make the system compact. In addition, it increases the flexibility to add more functions by increasing the total structure thickness without increasing the footprint size. However, it is more challenging to design and fabricate multilayer phased array. The vertical transitions between layers require careful design to have low loss and conventional fabrication technique may not be cost effective. Additive manufacturing (AM), which enables 3D objects of arbitrary shape to be printed automatically layer by layer, is a potentially promising technique to manufacture multilayer phased array that has reduced size and cost but still possesses good electromagnetic performance.