The seed germination of Laguncularia racemosa and Avicennia germinans, was assessed to know the growth of seedlings under controlled conditions at different intensities of shadow (0, 35, 50 and 75% darkness). Previously selected seeds were used from random trees located in Ciudad del Carmen Campeche. L. racemosa shows an average value in the seed weight of 0.69 g, 2.26 cm length and 1.19 cm width, for A. germinans, the average seed weight was 3.79 g, 3.26 cm long and 2.20 cm wide. L. racemosa germination began at 11 days, while in A. germinans, it began at 9 days. At the end of the evaluation, the germination percentages were 22.62% for A. germinans and 65% for L. racemosa. Moreover, the results indicated that at increasing darkness levels for both species; stem length can increase, compared with the control that was full sunlight. Apparently, the seeds of A. germinans do not tolerate high light intensities; a trend also observed in seedlings, because they show a high rate of mortality and consequently, a lower germination percentage compared to L. racemosa. The results can be useful to propose regeneration activities in natural mangroves of the tropical area of Mexico.