Correlating mechanical performance with mesoscale structure is fundamental for the design and optimization of light and strong fibers (or any composites), most promising being those from carbon nanotubes. In all forms of nanotube fiber production strategies, due to tubes’ mutual affinity, some degree of bundling into liquid crystal-like domains can be expected, causing heterogeneous load transfer within and outside these domains, and having a direct impact on the fiber strength. By employing large-scale coarse-grained simulations, we demonstrate that the strength s of nanotube fibers with characteristic domain size D scales as s ~ 1/D, while the degree of longitudinal/axial disorder within the domains (akin to a smectic ↔ nematic phase transition) can substantially mitigate this dependence.