Background: Radical cholecystectomy is recommended for T2 gallbladder cancer. However, it is unclear whether hepatic resection is essential for peritoneal-side gallbladder cancer. Methods: From January 2000 to December 2011, we identified T2 gallbladder cancer patients who had undergone curative intent surgery. A peritoneal-side tumor was defined when the epicenter of the tumor was located within the free peritoneal-side gallbladder mucosa. Hepatic-side gallbladder cancer was defined when the epicenter of the tumor was located within the gallbladder bed or neck. Results: A total of 157 patients with T2 gallbladder cancer were included; 33 peritoneal-side and 124 hepatic-side tumors. In total, 122 patients underwent hepatic resection, whereas the remaining 35 patients did not. After a median follow-up period of 40 (range 5–170) months, the survival of the peritoneal-side group was better than that of the hepatic-side group (p = 0.002). In a multivariate analysis, tumor location, lymph node metastasis, hepatic resection, lymphatic invasion, and perineural invasion were significant prognostic factors (p = 0.045, p < 0.001, p = 0.003, p = 0.046, and p = 0.027, respectively). For the peritoneal-side group, there was no recurrence or death after cholecystectomy without hepatic resection. However, hepatic resection was an important factor associated with overall survival in patients with hepatic-side gallbladder cancer (p = 0.007). Conclusions: In T2 gallbladder cancer patients, hepatic resection is recommended when there is tumor invasion of the gallbladder bed or neck. However, it is not always necessary in selected patients with peritoneal-side gallbladder cancer.