<p>Printability is fundamental to achieving excellent mechanical and durability properties in 3D-printed geopolymer (3DPG) structures. However, a systematic analysis of the printability of 3DPG is still lacking. This paper clarifies the critical role of raw material composition and printing parameters on pumpability, extrudability, and buildability based on the 3D printing process. It reviews how key components influence conventional printability indicators, such as flowability, setting time, and rheology, and discusses the mechanisms behind these effects. Direct evaluation metrics for extrudability and buildability are also examined. The findings indicate that the physicochemical properties of the precursor and the kinetics of its dissolution–condensation reaction, which forms the gel network, decisively influence the rheological properties. The activator controls rheology by balancing the kinetics of precursor dissolution, the nucleation and growth rates of the gel phase, and the formation and stability of the final micro-network. Chemical additives enable precise control over rheology by altering the reaction kinetics and the paste’s microstructure through physicochemical interactions such as adsorption, complexation, and nucleation. Furthermore, fibers can form a three-dimensional network that significantly increases yield stress and viscosity, reduces flowability, and enhances thixotropy, while having a minimal effect on the setting time. Finally, the future prospects of 3DPG are outlined, with constructive suggestions proposed. Future work should focus on developing mix-design optimization methods grounded in printability criteria and on leveraging green manufacturing technologies to make 3DPG printing more efficient and intelligent.</p>