Visual access has long been considered crucial for interpreters, providing essential kinesic cues such as gaze and facial expressions that enhance understanding and emphasis. Despite its acknowledged importance, empirical studies examining the impact of visual access on interpreters' performance remain limited. To date, conclusive evidence establishing a direct link between visual access and interpreters' performance is lacking. This study addresses this gap by employing a data-driven approach to explore the influence of visual components in source speeches on interpreting performance. A total of 48 graduate interpreter trainees (first language/L1: Chinese, second language/L2: English) participated in English-to-Chinese simultaneous interpreting tasks under both video and audio-only conditions. Two raters (L1: Chinese, L2: English) assessed their performances using three criteria: fidelity, target language quality (language), and fluency of delivery (delivery). Data analysis revealed that, overall, participants exhibited superior performance under the video condition (M = 4.92, SD = 1.62) compared to the audio-only condition (M = 4.19, SD = 1.67). Specifically, their performance in both fidelity and delivery was notably higher under the video condition (fidelity: M = 5.12, SD = 1.59; delivery: M = 4.58, SD = 0.23) than under the audio condition (fidelity: M = 4.38, SD = 1.63; delivery: M = 4.00, SD = 0.20). However, no statistically significant difference was observed in language performance between the two conditions. The implications are discussed at the end.