Along with the evolution, physical activity continues to decrease, espsecially in medical students. Aside from the benefits of physical activity, several journals have proven its positive effects on cognitive function and academic achievement. The relationship between physical activity and academic achievement has been widely studied in children, adolescents and older adults, but researches in productive age groups is still very rare and with inconsistent results. This research uses cross-sectional method and samples are third year medical students of Pelita Harapan University aged 18-22 years old chosen by simple random sampling. The sample size was calculated using correlative analytic formula. Physical activity is assessed using Global Physical Activity Questionnaire version 2 (GPAQ2). Academic achievement is measured based on students’ grade point and block scores. Research data is further processed using Microsoft Excel 2016, analyzed using Statistical Package for the Social Sciences (SPSS) and statistically tested using correlation and Chi- Square. The correlation between physical activity and academic achievement in third year medical students of Pelita Harapan University is negatively correlated, however very weak and not significant / Seiring perkembangan zaman, tingkat aktivitas fisikpun makin berkurang, khususnya pada populasi mahasiswa fakultas kedokteran. Tidak hanya bermanfaat bagi kesehatan, sejumlah jurnal penelitian membuktikan adanya efek positif aktivitas fisik terhadap fungsi kognitif dan prestasi akademik. Hubungan aktivitas fisik terhadap prestasi akademik telah banyak diteliti pada anak, remaja dan lanjut usia, namun penelitian pada orang dewasa usia produktif masih sangat jarang dengan hasil yang tidak konsisten. Penelitian dilakukan dengan metode potong lintang dengan sampel penelitian merupakan mahasiswa tahun ketiga Fakultas Kedokteran Universitas Pelita Harapan berusia 18-22 tahun yang dipilih dengan teknik simple random sampling. Besar sampel dihitung dengan rumus analitik korelatif. Aktivitas fisik dinilai menggunakan Global Physical Activity Questionnaire version 2 (GPAQ2). Prestasi akademik diukur berdasarkan Indeks Prestasi (IP) dan nilai blok mahasiswa. Data penelitian dianalisis menggunakan Statistical Package for the Social Sciences (SPSS) menggunakan metode uji korelasi dan Chi-Square. Korelasi antara aktivitas fisik dan prestasi akademik pada mahasiswa tahun ketiga Fakultas Kedokteran Universitas Pelita Harapan bersifat negatif, sangat lemah dan tidak signifikan.