Background: Flexible endoscopic procedures in the gastric cavity are usually performed by operative instruments introduced through the working channels of a gastroscope. To enable additional functions and to widen the spectrum of possible surgical procedures, assistive internal surgical instruments (AISI) may be deployed through the esophagus and fixed onto the gastric wall for the entire duration of the procedure. This paper presents a solution for deploying, positioning, and anchoring AISI inside the stomach by exploiting a chemical approach. Methods: A mucoadhesive polymer was synthesized and tested inside the stomach. In vivo trials were performed on a porcine model by introducing the AISI provided with mucoadhesive by means of an overtube through the mouth. Targeted deployment was achieved by a purposely developed delivery device, passed through the operative channel of a gastroscope. The total time for deployment, positioning, and anchoring of the AISI was evaluated by testing the procedure with passive modules (10, 12, 15, 20 mm in diameter) and active devices: e.g., a miniaturized wired camera and a wireless illumination module. The time and force required for the detachment of the modules were measured. Results: The whole procedure of in vivo deployment, positioning, and attachment of an AISI was performed in approximately 6 min. A preload force of 5 N for 3 min was required for anchoring the modules. The stable adhesion was maintained for a maximum of 110 min. Thanks to the positioning of the camera in the fundus, a wide view of the gastric cavity was obtained. The force required to detach the modules reached 2.8 N. Conclusions: Mucoadhesive anchoring represents a completely biocompatible and safe solution for stable positioning of AISI onto mucosal tissue. This novel polymeric mechanism can be useful for designing intraluminal accessories and tools that enhance surgeons' performances in endoluminal procedures.