Cognitive load in interpretation can be defined as the limited cognitive capacity that an interpreter devotes to the assigned task (e.g., Bóna & Bakti, 2020; Chen, 2017). Code-switching (CS), featuring the switch between languages in a single utterance, can be frequently noticed in daily conversations of bilinguals (Ng & Yang, 2022). When such habitual language use is not allowed among bilingual interpreters, it might negatively influence the interpretation performance (Cheung, 2001). While considerable number of studies investigated the cognitive load in CS processing (e.g., Hui et al., 2022; Moreno et al., 2002) and production (e.g., de Bruin et al., 2018; Kleinman & Gollan, 2016), limited research investigated the similar phenomenon in interpretation or translation. Researchers usually involved translation task in experiments (Price et al., 1999) or invited simultaneous interpreters as participants (Proverbio et al., 2004). However, among these studies, either the stimuli lacked naturalness for the interpreters, or the habitualness of the CS words was ignored. In Cheung’s (2001) study, it has been found that code-switching can be used as an effort management strategy to increase the accuracy, fluency, and completeness during interpretation. Nonetheless, the study used a university president’s welcome address as the instrument: the formality made it hard to evaluate the commonness of the chosen English code-switching words. In addition, only general parameters of audio data and evaluation from raters were included in the data analysis, leaving the results unreliable and incomprehensive. Focusing on sight translation as a variant of simultaneous interpretation (Pöchhacker, 2004) and the multi-cultural context of Macao, this research aimed to explore the influence of commonly code-switched English words in source text on cognitive load during English-Cantonese sight translation. The results suggested that higher cognitive load can be identified in condition where interpreters were not allowed to code switch than condition where they were allowed to do so.