The reactions of 2-methyl-1,4-naphthoquinone epoxide toward nucleophiles are studied here. In our study, 2-methyl-1,4-naphthoquinone epoxide was reacted with two nucleophiles: sodium azide and sodium thiocyanate in methanol. In the reaction of sodium azide and 1,4-naphthoquinone epoxide in methanol, the primary product was 2-azido-3-methyl-1,4-naphthoquinone, which was, in turn, quickly converted to another substitution product, 2-methoxy-3-methyl-1,4-naphthoquinone. In the presence of acid, however, 2-azido-3-methyl-1,4-naphthoquinone was isolated as the final product. Additionally, we found that the azide in the primary product further reduced to an amino group in the presence and absence of acid. In acidic conditions, sodium thiocyanate and 1,4-naphthoquinone epoxide reacted to form 2-methyl-3-thiocyano-1,4-naphthoquinone. The presence of acid in the reaction was found critical to form the product with fewer impurities. In the absence of acid, the reaction of 1,4-naphthoquinone epoxide and sodium thiocyanate did not give the 2-methyl-3-thiocyano-1,4-naphthoquinone as was formed in acid. Thus, our results show nucleophilic additions of azide and thiocyanate that occur on 2-methyl-1,4-naphthoquinone epoxide to be affected by the presence of acid.