The mango is a species that produces recalcitrant seeds, which can be difficult to store. The objective of this work was to evaluate the effect of storage period and mass on the germination of Carabao mango seeds. The fruits were picked and the pits were dried. The seeds were weighed and separated in two classes: I) with a mass up to 19.0g, and II) above 19.0g. The seeds were treated with 60% thiabendazol, wrapped in perforated transparent polyethylene bags, maintained in a laboratory, and germinated directly in the plastic bags. The statistical analysis used a randomized block design, with four repetitions, that consisted of five storage periods: 0 (zero), 7, 14, 21 and 28 days. A regression analysis was made. Due to the small number of seeds with a mass less than 19.0g, the germination tests using two classes were done only for the periods of zero and the first seven days of storage. It was found that the seeds of Carabao mango, when treated with fungicide, performed best when sown after seven days of storage in polyethylene bags, and that the mass of the seeds positively influenced germination.