Previous research using the Visual World Paradigm (VWP) has shown that sentence processing is influenced by the visual environment in which sentences are presented. This study investigates the online processing of the syntactic complexity and linear distance in Turkish sentence processing through an eye-tracking experiment employing the VWP. Specifically, we examined how auditory-visual information interacts with syntactic complexity (nested vs. linear) and sentence distance (short vs. long). We hypothesised that (1) auditory-visual information is sensitive to online processing of syntactic complexity in subject-relative clauses (SRCs), (2) the linear distance between preverbal and postverbal positions is critical for incremental processing between long-short sentences, and (3) the syntactic information and working memory (WM) may share separate mental representations during online sentence processing. The experimental stimuli included 240 sentences, of which 120 were experimental and 120 were filler sentences. 57 Turkish participants were randomly presented with the auditory-visual stimuli. Our findings showed that syntactic complexity significantly affected gaze durations, with longer fixations obtained for nested compared to linear structures. Additionally, the linear distance between preverbal and postverbal positions showed a distinct effect: participants fixated longer on preverbal positions in short sentences than in long sentences. Notably, a forward digit-span task conducted before the main task did not indicate an interaction between WM capacity and syntactic processing, suggesting that these mechanisms may operate with separate cognitive representations. Overall, these results highlight that syntactic complexity leads to longer fixations in nested structures, linear distance influences fixation durations with longer durations for preverbal positions in short sentences, and WM and syntactic processing appear to function independently during online sentence processing.