Defensive armor has repeatedly evolved among animals. There is a trade off between flexibility and defense, and heavy armor is costly due to the energetic investment of swimming with, maintaining, and growing densely mineralized scales or plates. Armor can also stiffen the body for locomotion or serve as an elastic storage mechanism. Each role has an influence on what the armor is made of, and how elements connect and interact. Poachers (Agonidae) are cottoid fishes with heavy, overlapping armor plates that provide protection from harsh environments, aggressive conspecifics, and predators. The overlapping nature of these armor plates ensures there are no gaps in protection, while still facilitating locomotion. We measured plate overlap from micro-computed tomographic scans of straight and bent spearnose poacher (Agonopsis vulsa). We described the microstructure of the plates and the area between plates by sectioning and staining. There is considerable antero-posterior overlap (~15% plate area) among plates in compression, and in tension there is less overlap (~7% plate area). Differences in lateral overlap were negligible between bent (compression) and straight specimens, but increased between rows when in tension. Overlap among neighboring plates varies in magnitude depending on the direction of overlap. For example, the degree of movement in an antero-posterior direction is more limited than lateral overlap due to a tongue and groove rail system along the underside of the plate’s surface. Histology shows that A. vulsa scales are primarily composed of acellular bone and there is connective tissue between overlapping plates. The presence of this connective tissue, which may act as an elastic brake, implies a sophisticated system of movement and positioning between plates during bending.