Coarse-grained molecular dynamics simulations have been performed to investigate the tensile behavior of CNT films. It is found that CNT entanglements greatly degrade the tensile load-bearing capability of CNT films. The effect of twisting on the tensile behavior of CNT fibers spun from CNT films has also been investigated. Results indicate that twisting can make either positive or negative contributions to the mechanical properties of the film, depending on the microstructure. The structural and energy evolution of CNT films and fibers, as well as the stress distributions of CNTs which cannot be easily determined experimentally, have been illustrated. This study provides an effective means of revealing the structure/property relationships of CNT films/fibers, which are essential in designing high performance CNT fibers.