Direct Metal Laser Sintering (DMLS), considered here as a process-specific implementation of laser powder bed fusion (LPBF), produces Ti6Al4V with a fine acicular α′-type morphology, high hardness, residual stresses and orientation-dependent mechanical behaviour. This study quantified the effect of annealing temperature on the coupled evolution of microhardness, Charpy impact toughness, mechanical anisotropy and fracture morphology. Ti6Al4V ELI specimens were fabricated in XY and XZ orientations at a volumetric energy density of 127 J/mm³ and annealed at 650, 750, 850 or 950 °C for 2 h under argon. Mechanical response was evaluated by HV5 measurements (at least nine indentations per measurement plane), Charpy testing (n = 3 per heat-treatment condition and orientation), and SEM-based microstructural and fractographic assessment. At 950 °C, perpendicular-plane hardness decreased by 18.8% (401.7 ± 20.8 to 326.0 ± 5.6 HV5), whereas mean impact toughness increased by 266.8% (14.29 ± 2.50 to 52.41 ± 8.50 J/cm²). The hardness anisotropy coefficient decreased by 5.8%, from 1.078 to 1.015, and the impact-toughness anisotropy coefficient decreased by 26.2%, from 1.397 to 1.031. SEM observations showed a progressive transition from defect-sensitive quasi-brittle fracture toward predominantly ductile microvoid coalescence. Annealing at 850–950 °C therefore produced the most favourable balance between retained hardness, enhanced impact resistance, reduced orientation dependence and ductile fracture behaviour.