This study investigated how availability of attentional resources and listeners' inhibitory control (IC) affect cue weighting in L2 vowel categorization and whether the effects vary with L2 proficiency. Thirty-five Chinese L2 learners of English categorized sounds from the English /ɛ/-/æ/ and /i/-/ɪ/ continua under low and high load. IC and L2 proficiency were measured using the Stroop task and LexTALE. Group results showed that learners used primarily spectral quality and secondarily duration for both contrasts, with spectral reliance increasing with L2 proficiency. /i/-/ɪ/ categorization exhibited stronger warping effects of short (vs long) duration on spectral use, particularly for high proficiency learners. High load induced lower spectral reliance across both contrasts, with duration warping effects in /i/-/ɪ/ categorization being more pronounced under low (vs high) load. Learners with weaker IC were more susceptible to load-induced reduction in spectral use and exhibited stronger duration warping effects. Neither attentional variable interacted with L2 proficiency in affecting L2 cue weighting. Our findings support a hierarchical model of attentional modulation in L2 cue weighting where cognitive load directly impairs reliance on the strong cue, while IC operates as a protective factor that mitigates the severity of the load-induced impairment in difficult L2 contrasts.