This study set out to investigate the impact of logical metafunction on syntactic complexity, and in doing so, it also measured the extent to which it impacted syntactic complexity. This study applied a one-group pre-test post-test experimental research design on 30 participants across a span of 40 sessions. To measure syntactic complexity, L2SCA accessed through TAASSC was used. A paired-sample t-test was employed in samples to make comparison of syntactic complexity deduced from the 14 indices. Furthermore, the study measured the Cohen's d values to discern the practical implication within the mean differences observed. A substantial enhancement in all indices of syntactic complexity was noted, except for one index (CP/C) which had a moderate effect. The study proved that this theory can be used by ESL educators and learners to make their writings logically connected and complex, resulting in marked enhancement of academic writing skills and language proficiency.