Laser technology often offers solutions where existing technologies have struggled or require improvements. Over the last two decades, laser transmission welding (LTW) has become a viable fabrication method for industries that engaged in polymer welding. This paper presents a comprehensive review on several aspects of LTW process. In specific, this review focuses on four major aspects of the LTW: (a) process fundamentals, including operating principles and process requirements; (b) compositions and pre-welding conditions of polymers and their effects; (c) laser weldability of polymers, considering compatibility and non-compatibility issues; and (d) welding techniques and application strategies, including technological variants and the transformation of application strategies from absorber-based to absorber-free laser welding of polymers. The conclusion of the review and the prospects for further research work are eventually addressed.