Major research efforts have gone into investigating whether and when bi- and multilinguals exhibit advantages in domain-general executive control (EC) functions compared to monolinguals. While a large body of evidence suggests that multilinguals are continually exposed to language conflict, the consequences of managing language conflict for EC remain disputed. Against this backdrop, simultaneous interpreting (SI) emerges as a suitable paradigm to test how language control (LC) might affect EC: As SI requires source language comprehension and simultaneous target language production, both languages must be highly activated, while disruptive interference must be suppressed. SI thus relies on an extreme form of LC. If LC mechanisms affect EC, the constant and extreme LC required during SI could result in quantifiable changes in interpreters’ EC measures. A longitudinal investigation comparing 14 interpreting trainees to 14 translation trainees without SI training was carried out to investigate potential SI-induced changes of LC and EC abilities. To dissect the assumed relationship between verbal and non-verbal cognitive control, measures from three tasks tapping EC and LC to varying degrees were taken: from a bilingual Stroop task, a trilingual number naming task and a language-independent number categorisation task. The post-training results revealed no between-group differences with regard to non-verbal control capacities, neither in terms of interference resistance nor with regard to task switching. Verbal control, however, improved in both groups with regard to interference resistance, while verbal task switching speed was unaffected in the control group, but partially increased in the experimental group.