Additive manufacturing (AM) is a powerful and promising manufacturing technology. Advances in AM have led to increasing demands for its applications; however, controlling the geometry of deposited objects during the AM process remains a major challenge. Geometry control and compliance to a target geometry are some of the key concerns for AM, especially for a prototype requiring high precision in its geometry. In this study, an online geometry estimation methodology for continuous monitoring during the directed energy deposition (DED) process was developed using a laser line scanner. Our proposed methodology comprises (1) real-time scanning of each deposited track's profile, (2) online extraction of the track's geometry, and (3) online plotting and comparison of the as-designed and as-built models. In the methodology, data analysis following real-time scanning, such as geometry discrepancy estimation and online plotting of the as-built model, is attained for both single- and multi-layer objects. The effectiveness of our developed methodology is examined by comparing the profiles of the single- and multi-layer objects estimated during the DED process with the reference profiles obtained via laser line scanning and microscopy after the completion of the DED process.