One of the major limitations of the current 3D-concrete-printing technology is the incorporation of reinforcement. Furthermore, there is a need to decrease the ecological footprint of printable concrete. As a possible solution for these challenges, this paper presents a 3D-printable strain-hardening alkali-activated composite (3DP-SHAAC) that shows pseudo-ductile behaviour under direct tension. The developed 3DP-SHAAC is composed of a one-part (just-add-water) alkali-activated binder made of slag (GGBFS), fly ash (FA) and solid activators. The one-part alkali-activated binder eliminates the need for elevated temperature curing and handling of corrosive alkaline liquids. At first, an optimum matrix was identified by studying the effects of FA to GGBFS ratio on the rheological properties and compressive strength. Subsequently, the optimum matrix was reinforced by PVA fibres to make the 3DP-SHAAC, and printing performance and rheological properties were evaluated. In addition, the influences of curing temperature on the compressive, flexural and tensile performances of the printed specimens were also investigated. The results were compared with those obtained for the mould-cast specimens. The 3DP-SHAAC exhibited superior flexural performance, higher tensile strength, and comparable tensile strain capacity to the mould-cast counterpart. Further, the curing temperature had influence on the mechanical properties of both 3D-printed and mould-cast SHAACs. The underlying reasons for the differences are discussed.