With this paper we analyze the correlation between the degradation of InGaN-based laser diodes (LDs) and the increase in the non-radiative recombination rate in the active region. Several 405 nm MOCVD LDs have been submitted to CW stress, for 2000 h (stress current in the range 40–100 mA, case temperature = 75 °C). During stress, we extensively evaluated the optical characteristics of the LDs: a technique for the evaluation of the non-radiative recombination lifetime (τnr) in the active material was developed and used for the analysis of the stress effects. We demonstrate the following: (1) degradation determines the increase in LDs threshold current (Ith) and the decrease in the τnr; (2) degradation of Ith and τnr have similar kinetics; and (3) the degradation rate of the LDs is almost linearly related to the stress current level. The degradation process is therefore ascribed to the decrease of internal quantum efficiency caused by the increase of the non-radiative recombination rate in the active region.