Abstract Resolving sentence ambiguity demands precision thus, this study examines the sentence processing strategies of Kolibugan secondary learners when interpreting syntactically ambiguous English sentences involving relative clause attachments. Employing a sequential explanatory design, 56 participants were grouped by English proficiency and assessed through comprehension tasks and follow-up interviews. Quantitative results show a consistent low attachment (LA) preference across groups, with stronger LA bias among low-proficiency learners. Qualitative findings indicate that learners heavily relied on L1-based strategies, including direct translation, linear parsing, and syntactic restructuring grounded in Kolibugan grammar. These outcomes align with the Garden Path Model and Shallow Structure Hypothesis illustrates the influence of L1 transfer and limited syntactic access in L2 processing. The study further emphasizes the adaptive nature of parsing behavior shaped by cognitive constraints, proficiency level, and language exposure. Recommendations include integrating metalinguistic awareness and comparative grammar approaches in English instruction. Furthermore, pedagogical implications stress the need for explicit syntactic awareness instruction and culturally responsive approaches tailored to underrepresented linguistic communities. Keywords: sentence parsing, syntactic ambiguity, Kolibugan, garden-path, shallow hypothesis