<p>Fused deposition modelling (FDM), a widely used 3D printing technique, is employed to fabricate acrylonitrile butadiene styrene (ABS) specimens, selected for its reliable printability and sensitivity to processing conditions. The flexibility of FDM enables precise control over printing parameters, providing an effective platform to examine their influence on fracture behaviour. In this study, the effects of layer height, nozzle diameter, and print speed are systematically investigated using the essential work of fracture (EWF) method, which separates crack-initiation and crack-propagation energy contributions. A full factorial design of experiments is implemented, revealing strong agreement between fracture responses and morphological observations, thereby linking microstructural features to governing fracture mechanisms. The results show that layer height and print speed are the most influential parameters. Reducing layer height increased tensile strength, tensile modulus, and crack-initiation resistance by approximately 15%, 11%, and 74%, respectively. Similarly, lower print speed improved these properties by about 6%, 4%, and 20%. Accordingly, optimal tensile and fracture performance was achieved at low layer height and low print speed, while nozzle diameter showed a comparatively minor effect. Conversely, higher layer height, higher print speed, and larger nozzle diameter enhanced ductility and crack-propagation resistance, highlighting a trade-off between strength-dominated and energy-dissipative fracture behaviour. These findings provide practical guidelines for tailoring fracture performance in FDM-printed ABS.</p>