It was suggested that processing subject relative clauses (SRCs) are universally easier than processing object relative clauses (ORCs) based on the studies carried out in head-initial languages such as English, and German. However, studies carried out in head-final languages such as Chinese and Basque refuted this claim. Turkish is also a head-final language. Existing relative clause processing literature in Turkish is based solely on behavioural metrics. Even though an ORC processing disadvantage was suggested for Turkish, the results were not conclusive. Therefore, we aimed to investigate the neural dynamics of relative clause processing in Turkish. We asked 14 native Turkish speakers to answer Yes/No questions about 24 sentences each containing either SRC or ORC while their prefrontal hemodynamic activity was recorded with fNIRS. Our findings revealed hemodynamic activity in the lateral portions of the left prefrontal cortex in both conditions. However, hemodynamic activity was more widespread in prefrontal regions for ORC than SRC. Even though the behavioural metrics failed to produce a significant difference between SRC and ORC conditions, direct ORC>SRC contrast revealed significant activity in left and right DLPFC, which are known to be involved in language processing and conflict monitoring related processes, respectively. Our findings indicate that processing ORCs are more difficult and require further prefrontal resources than processing SRCs in Turkish, thus refuting the head-directionality based explanations of relative clause processing asymmetries.