This study aimed to investigate the effectiveness of carrageenan (CGN) as an oral immune adjuvant. During the initial research, the inadvertent shallow insertion of an oral gavage needle confirmed CGN’s effect as an adjuvant for esophageal immunization. However, in oral immunization, antibody formation was not observed regardless of CGN’s presence or absence as an adjuvant. Conversely, when bovine serum albumin (used as an antigen) was introduced into the esophagus along with CGN, it resulted in the production of antigen-specific IgG. An exploration was conducted to ascertain whether CGN’s adjuvant effects were associated with prolonging the antigen’s residence time in the esophagus. Upon introducing the antigen into the esophagus without CGN, it was undetectable at two minutes post-introduction. Conversely, when administered with CGN, the antigen remained detectable in the esophagus for up to five minutes post-introduction. To investigate whether this immune response was elicited through mucosal immune mechanisms in the esophagus, the production of IgA, a representative immunoglobulin of mucosal immunity, was assessed. Following esophageal immunization with CGN as an adjuvant, total IgG, IgG1, and IgG2a were detected in serum, while IgA was not detected. These findings suggest that under specific conditions, the esophagus may serve as a site for initiating a novel immune response.