Second language learning requires conscious and persistent efforts on the part of the learner, to achieve significant proficiency. Generally, students show complacency towards learning a new language, as a result of frustrating factors such as unfamiliar vocabularies, mixing words with different textual meanings, difficulties in adopting the mechanics of effective writing and others. The dictionary as a learning resource, helps in ameliorating these challenges; serving as a complementary aid for learners, and even teachers in the choice of pedagogic strategies. The methodology adopts a quantitative design in assessing the effectiveness of the use of dictionaries, amongst secondary school teachers and students in Nigeria, using appropriate questionnaires. The result revealed the indispensable role of the dictionary as a learning resource in an ESL environment, and its maximal benefits when students are proactively trained to use it.