We present a combined theoretical, numerical and experimental investigation on trap-assisted tunneling (TAT) in the subthreshold regime of III-nitride-based light-emitting diodes (LEDs). Starting from the basic formulation of the TAT models provided by Hurkx and Schenk, we discuss the derivation of a detailed approach based on both multiphonon and elastic nonlocal processes. A sensitivity study conducted over the main trap- and phonon-related physical parameters of this nonlocal TAT model confirms the importance of tunneling assisted by lattice defects on the LED electrical behavior in the low-medium forward bias range. Comparisons with measured temperature-dependent electrical characteristics I(V;T) of a single quantum well LED grown on a highly conductive SiC substrate demonstrate that I(V;T) can be accurately reproduced in the range between 200 and 400 K by implementing the nonlocal model for TAT processes via traps in the electron-blocking and spacer layers. © 2015, Springer Science+Business Media New York.