Purpose: This study evaluated the effects of noise and speech intelligibility on the processing of speech produced from native English; high-intelligibility, Korean-accented English; and moderate-intelligibility, Korean-accented English speakers. Method: Both listener comprehension, determined by accuracy judgment on true/false sentences, and processing time, estimated from response latency, were assessed under the following 3 conditions: quiet, +10 dB signal-to-noise ratio (SNR), and +5 dB SNR. Fifty-four monolingual, English-speaking adults served as the listeners for this study. Results: While noise did not affect the time it took to process foreign-accented speech, it decreased the comprehension of the foreign-accented speech more so than the native speech. Decreasing English intelligibility also resulted in reduced listener comprehension. In addition, the processing time needed to comprehend the intended message depended on the intelligibility of the foreign-accented speaker. Listener comprehension negatively correlated with processing time. Conclusion: The findings suggest that decreased speech intelligibility and adverse listening conditions can be major challenges for effective communication between foreign-accented speakers and native listeners. The results also indicate that foreign-accented speech requires more effortful processing relative to native speech under certain conditions, affecting both comprehension and processing efficiency.