The tetrazolium test has been recommended for evaluating the viability of seeds with slow and ununiform germination, especially agroforestry species. The aim of this study was to propose a methodology to evaluate the viability of J. curcas L. seeds using the tetrazolium test and to generate visual aids to support the interpretation of the test. In the first trial, methods of seed preparation and staining were evaluated. The most promising methodologies were used to conduct the second test, which consisted of the evaluation of different concentrations (0.10 and 0.25%) and times (2 and 3 h) of immersion of the seeds in the tetrazolium solution, using five lots. The seeds were analyzed individually and classified as viable or non-viable. At the same time, germination, first count, emergence and seedling emergence speed index tests were conducted. The tetrazolium test is efficient for evaluating the viability of seeds of J. curcas L. providing results correlated with germination and seedling emergence. Pre-soaked seeds should have their integument removed and then sectioned longitudinally and medially lengthwise for immersion in 0.10% solution of 2,3,5-triphenyl chloride tetrazolium for three hours at 35 °C.