This study aimed to assess the mangrove species and to measure the carbon dioxide sequestration in the coastal areas of Tangub City. This study utilized the descriptive evaluative survey. The purposive sampling technique was used to assess the mangrove species through the identification of individual based on CVCIRRD Primavera 2000. Every mangrove species in the sampling areas was determined and the carbon dioxide sequestrations rate was measured based on algorithm. There were eight (8) species under of the five (5) families. The four (4) coastal barangays in Tangub City are still in state of moderate diversity with the value of 0.7508 for Lorenzo Tan, 0.6931 for Maquilao, 0.7525 for Garang and 0.6479 also for Maloro but in minimal level. The mangrove forest sequestered more than the amount of 31,505,143 pounds or more than 14.2 million kilograms of carbon dioxide. The relationship between the mangrove population and carbon sequestration was measured using the Pearson’s correlation and the result revealed an r-value of 0.944 with perfect correlation as giving by the degree of correlation. Meanwhile, the p value 0.000 was less than tabular value 0.05 therefore, the relationship was statistically significant.