Applying discourse analysis within the framework of Systemic Functional Linguistics (SFL), this study offers a fresh reexamination of the textual and contextual relationship between First and Second Thessalonians. Through register analysis—a key component of SFL discourse analysis—it uncovers a unified linguistic profile across both letters, characterized by pastoral consistency, relational coherence, and structural clarity. By challenging traditional assumptions of textual and situational divergence, it offers a linguistically grounded evaluation of the Pauline authorship debate concerning the Thessalonian correspondence. Combining methodological rigor with accessibility, the study invites readers in New Testament studies, biblical linguistics, and early Christian discourse to engage these foundational Pauline letters—textually, contextually, and with renewed insight.