Abstract Trends in educational inequalities in adult (25 years old and over) gastric cancer mortality by sex and age group in Colombia from 1998-2015 were analyzed. An ecological time series study was conducted using Colombian vital statistics and official population estimations. Age-standardized mortality rates (ASMR per 100,000 person-years) for gastric cancer were calculated separately by educational level, sex, and grouped age. A Poisson regression model was used to calculate rates ratios (RR) and the Relative Index of Inequalities (RII). The changes over time of the ASMR and RII were analyzed using a joinpoint analysis. During the study period, 80,520 deaths from gastric cancer were recorded among adults, 60% among men. Higher ASMRs were found in the lower educational levels. The inequality measured by the RII was lower among women compared to men. Young and middle-aged men suffered from the highest relative inequalities, while older men bore the toll of higher mortality rates and a greater increase in relative inequalities. It is necessary to address public health programs aimed at strengthening the quality of life of the populations identified as at risk of stomach cancer.