Listening to familiar voices might improve intelligibility of target speech in multiple-talker situations. In addition to personally familiar voices, voice training—through implicit exposure or explicit learning of a previously unheard voice—can improve speech intelligibility. However, there is no consensus on which method is more effective. We investigated the effect of explicit and implicit voice training on speech-on-speech perception and listening effort (pupillometry), among normal hearing listeners. There was no significant difference in speech intelligibility performance between trained and untrained voices, with either voice training method. However, an interaction between voice training method and target-to-masker ratio (TMR) on accuracy scores showed that the benefit of increased TMR on accuracy scores was significantly larger when voice training was implicit compared to explicit. Pupillometry results showed that explicit voice training significantly reduced listening effort for most disadvantageous TMR (−6dB), but not for more advantageous TMRs (0 and + 6 dB), and not for implicitly trained voices. Our results may imply that explicit voice training is more effective than implicit voice training in reducing listening effort. Still, implicit voice training, perhaps via procedural learning, might be more beneficial on the performance level when TMR becomes more advantageous.