This quasi-experimental study aimed at identifying the effect of words sort in the vocabulary development in mother tongue among the grade three pupils. Using the one-group pre-test design, the researchers exposed the participants in the word sort activities within fifteen(15)hours intervention. The participants of the study were the twenty(20) grade three pupils enrolled at Leganes central elementary school S.Y. 2015-2016. Fast-writing activity was initially done among the grade three pupils to find out the most commonly used words of the children and this was also used as the basis of making the pre-test and post-test questionnaire. They had undergone validation from the experts in mother tongue-based multilingual education. The top ten commonly used words in hiligaynon were libro, papel, ido, kuring, mata, dahon, sapatos and itlog. The descriptive statistics employed were the means and standard deviations to measure the word sort level before and after the intervention. To test the significant difference between the pre-test and post-test level of word sorting, the researchers employed the wilcoxon signed rank value set at 0.5 level of significance. The results revealed that there was a increase in the mean score of the participants after the intervention. Prior to the conduct of the intervention, the word sort level of the participants was good (M=19.90 SD=1.68). After the intervention, the participants acquired an excellent rating (M=26.25, SD=2.79). There was a significant difference on the word sort level, z=-3.86, p=<05. The result further explained that the group improve their word sort level after they were exposed to word sort activity.