In this paper, we propose a technique by integrating mechanical mounts into lens elements to fulfill a self-aligned and self-assembled optical system. To prove this concept, we designed, fabricated, and tested an ultra-compact endoscope that adopts this technique. By taking advantages of the specially designed fixture and observing the interference fringes between the lens and fixture, we developed a method to minimize decenter and tilt between the two surfaces of the endoscope lens during the diamond turning fabrication process. The integrated mechanical mounts provide an easy assembly process for the endoscope system while maintaining high accuracy in system alignment. With the application of heat shrink tube as the endoscope system holder and to block stray light, the proposed endoscope system has the advantages of low cost, compact size, and high imaging quality.