Resonant tunneling intrinsically exists in disordered borophene nanoribbons (BNRs) with randomly distributed line defects (LDs), providing a versatile platform for transport modulation. Here, we theoretically investigate the effects of in-plane mechanical strain on the electronic transport properties of disordered BNRs coupled to metallic electrodes. Our results demonstrate that the resonant peaks in disordered BNRs of different widths remain robust against variations in electrode parameters and can be efficiently modulated via mechanical strain. Specifically, uniaxial strain significantly modulates the energies, widths, and amplitudes of these resonant peaks, and can even suppress the peaks selectively and induce new ones. In particular, the response of the resonant energies to the applied strain exhibits remarkable anisotropy, where strains along the longitudinal and transverse directions induce opposite energy shifts. Moreover, identical resonant peaks recurring in different nanoribbon widths respond uniformly to applied strain. Biaxial strain enables highly efficient conductance switching across multiple distinct levels, with the modulation frequency increasing for wider nanoribbons. Our findings establish a promising defect-strain-engineering strategy for manipulating electronic transport in borophene and other gapless materials.