3D concrete printing is increasingly being adopted in construction, yet limited knowledge exists on the creep behaviour of printed elements, particularly in the hardened state. This study presents an investigation into the short-term creep behaviour of 3D printed concrete (3DPC) under compressive stress. Printed samples reinforced with micro-synthetic polypropylene fibers were compared with conventionally cast samples of the same mix. A sustained load of 35% of the ultimate compressive strength was applied for 30 days to evaluate time-dependent deformation. The microstructural evolution of cast and printed samples was investigated using X-ray computed tomography, with particular focus on porosity and CT imaging to examine its influence on mechanical properties. Experimental results highlight pronounced anisotropy in the mechanical response of printed samples, with cylindrical samples reaching 75 and 76% of the compressive strength of cubic counterparts for cast and printed samples, respectively. Cast samples generally outperformed printed ones, while higher creep strains were recorded in printed samples, attributed to increased porosity and interlayer voids. These findings emphasize the need to account for creep in the hardened state when designing with 3DPC.