There is a sharp rise in the use of social networking sites (SNSs) by university students for various purposes. However, little is known about the use of SNSs for educational purposes. This study aims to determine educational use of SNSs by the medical students of two Saudi and a Kuwaiti medical school. A cross-sectional study was conducted by administering a 20-statement questionnaire to the undergraduate medical and allied health sciences students of two Saudi universities: Taibah University (TU) and Imam Abdulrahman AlFaisal University (IAFU), and one Kuwaiti university, Kuwait University (KU). The data were collected and analyzed by SPSS 20. Of a total of 1312 respondents, 1181 (90%) students used SNSs and 131 (10%) did not use SNSs for any reason. Further, only 442/1181 (37%, p < 0.00) students used SNSs for education and found these sites to be useful. As many as 357 (27%) students used SNSs for sharing education-related information once a day, 306 (23%) 3–5 times a day, and 331 (25%) once a week. A maximum of 678 (52%) used Facebook for educational purpose and most of the students, 469 (38%), used SNSs for sharing lectures. There were significant variations in responses among genders and year of schooling. The use of online social media in medical education is a rapidly evolving arena of scholarship. Low use of SNSs for sharing information and significant variations in perceptions of medical students about social media should draw attention of policy-makers for promoting awareness and educational reforms.