Objective: To identify distinctive 18F-FDG positron emission tomography (PET)/computer tomography (CT) features of gastric-type endocervical adenocarcinoma (GAS) that differentiate it from squamous cell carcinoma (SCC) and usual-type endocervical adenocarcinoma (UEA), as well as to correlate these findings with pathological characteristics. Methods: Patients treated between December 2018 and December 2024 were retrospectively reviewed. The study included 12 GAS, 48 SCC, and 30 UEA cases. Evaluated parameters included tumor morphology, cystic components, uterine cavity fluid, N/M staging, tumor diameter, the cervical lesion maximum standardized uptake value (SUVmax), and the tumor-to-liver maximum standardized uptake ratio (T/L SUVmax). Results: GAS predominantly exhibited diffuse infiltrative growth (11/12), in contrast to mass-like growth observed in SCC (37/48) and UEA (24/30) (both p < 0.001). Cystic components, uterine cavity fluid, and peritoneal metastasis occurred significantly more frequently in GAS (12/12, 11/12, 5/12, respectively) compared to SCC and UEA (all p < 0.001). Elevated CA19-9 levels were more common in GAS (9/12) compared with SCC (p < 0.001). Tumor diameter did not differ significantly among the groups (p > 0.05). SUVmax and T/L SUVmax values were significantly lower in GAS (7.5 ± 3.8 and 2.5 ± 1.6, respectively) than in UEA (19.1 ± 11.4 and 5.7 ± 3.4) and SCC (17.4 ± 6.7 and 5.5 ± 2.6) (all p < 0.001). Conclusion: The clinical characteristics of GAS include infiltrative tumor growth, fluid accumulation in the uterine cavity, frequent formation of microcystic or macrocystic components, peritoneal metastasis, and elevated CA19-9 levels. In this cohort, SUVmax and T/L SUVmax values in GAS were significantly lower than those observed in SCC and UEA.