Mean platelet volume (MPV) is an inflammatory marker indicative of platelet activation. There are several studies that suggest an association between the neoplastic process and cancer metastasis. We performed a retrospective analysis to investigate the role of MPV as a prognostic informative marker in gallbladder cancer. This study included 73 patients who underwent treatment for gallbladder cancer with curative or palliative intent. MPV was obtained and statistically analysed to investigate the association between the nodal status (N), the overall stage as per the American Joint Committee on Cancer (AJCC) staging system, perineural invasion, and differentiation of the tumor. The statistical analysis was done using SPSS Statistics, version 23 (IBM Corp., Armonk, NY). We found that the MPV values were significantly high in node-positive cases (OR = 3.623, 95% CI = 7.778-1.687, p value = −0.0001), cases in the advanced stage (OR = 3.623, 95% CI = 7.778-1.687, p value = 0.0001), cases with perineural invasion (OR = 3.396, 95% CI = 8.319-1.387, p value = −0.0001), and poor differentiation (OR = 2.327, 95% CI = 4.651-1.164, p value = −0.002 ). MPV is an inexpensive and convenient inflammatory marker that correlates with nodal positivity in the staging and prognostication of gallbladder cancer. This marker can be used to ascertain the risk status of gallbladder cancer.