Additive manufacturing (AM) offers significant advantages in the way of economics and material/shape flexibility. However, one primary drawback of AM technology is the difficulty in manufacturing fiber reinforced parts. We have recently developed an AM process for continuous glass fiber reinforced composites using a liquid crystal display (LCD) printer. The process allows for the inclusion of resin-rich layers (RRL) between plies to toughen the regions vulnerable to premature failure. This work aims to understand the effect of RRL properties and thickness on the interlaminar toughness of AM glass fiber laminates (i.e., Gic and Giic). We used a combination of microscopy and spectroscopy to investigate the failure process. Our results revealed that the resin used in the RRL significantly affected material properties. For example, we show that a brittle resin (DA2) in the RRL significantly compromised the interlaminar toughness due to microcracking. However, the use of a tough RRL (Tenacious) significantly increased Giic by ~90% and linearly improved the initiation Gic. The fractured surfaces were studied in detail, and the data suggests that the RRL laminate interface is critical for translating resin properties to the composite, thus improving laminate interlaminar toughness.