Background Vitamin D and calcium are essential dietary components for human body, and their deficiency is linked to poor bone health and osteoporosis. Adequate knowledge of health staff regarding vitamin D and calcium is critical for general population awareness. The current work was to evaluate the awareness regarding the importance of vitamin D and calcium among undergraduate health science students in Al Kharj. Methods A self-distributed validated questionnaire-based cross-sectional study was conducted. Undergraduate health science students in Prince Sattam bin Abdulaziz University from the College of Medicine, College of Pharmacy, College of Dentistry, and College of Applied Medical Science were included in the study. Students between the age of 18 and 25 years have participated in the study. Results Four hundred fifty-seven undergraduate health science students participated in the study. The vast majority of students knew about the importance of calcium (96.7%) and vitamin D (95.4%), whereas only 89.4% knew about osteoporosis. The participant students reported in their answers that the sources of knowledge were the Internet (42.8%), physicians (41.5%), textbooks (21.2%), teachers (19.1%), family and relatives (18.3%), and/or other sources (6.1%). The overall attitude was poor in about (54%) of the participants showing gender differences regarding sun-exposure duration and supplementation of calcium and vitamin D. Conclusion The study revealed that both male and female undergraduate health science students in Al Kharj were familiar with the importance of vitamin D and calcium; however they reported improper attitude that warrants further health guidance and educational programs.