This study investigated the effectiveness of internet accessibility on academic activities of open and distant learners of the National Open University of Nigeria, Lagos State. Technological Determinism Theory and Media Dependency Theory provided the framework for the study. A survey method was adopted, and a questionnaire comprising closed-ended and open-ended questions was used to collect data. It used a simple random sampling method in choosing the sample. One hundred twenty copies of the questionnaire were administered to the respondents during the study. Findings from the data analysed show that most students have access to the internet mainly on their mobile phones with self-sponsored mobile data. They face difficulties accessing the internet, which interferes with their academic activities. The study recommended that the National Open University of Nigeria should improve its network service to give the students seamless access to the school's online platforms and provide some offline options for the learners as alternatives to guard against any unexpected failure of the online options. The offline options will also carry along the older and less tech-savvy learners until they adapt to the online school system. The work concluded that poor internet accessibility significantly affects academic activities in open and distance learning. Consequently, access to the internet should be improved.