<p>Wire arc additive manufacturing (WAAM) offers a promising route for fabricating large-scale titanium alloy components in aerospace applications. However, the fatigue crack growth (FCG) behavior of WAAMed TC11 titanium alloy, particularly under different heat treatments, remains poorly understood. This study therefore investigates the influence of post-heat treatment on FCG performance in the Paris region. Four thermal cycles were applied to tailor the microstructure, and results show that post-heat treatment significantly affects FCG rates. The lowest crack growth rate was achieved in samples with equiaxed grains and multi-oriented colony microstructures, while all WAAM-heat-treated samples exhibited superior FCG resistance compared to laser melted deposited TC4-DT sample with lamellar microstructure. A linear relationship between the Paris exponent <i>m</i> and lg(<i>C</i>) was observed, indicating predictable FCG behavior. Additionally, crack growth mechanisms transition from quasi-cleavage at low Δ<i>K</i> levels (13 MPa m^1/2) to micro-void coalescence at high Δ<i>K</i> levels (40 MPa m^1/2), with reduced sensitivity to microstructure at higher stress intensities. These findings provide valuable guidance for optimizing damage-tolerant design of TC11 components in reusable launch vehicles.</p>