Introduction: Anemia is a significant health problem among adolescent girls. This study aimed to determine the prevalence, related factors, and knowledge about anemia among adolescent girls in a remote area of western Rajasthan. Methods: In a rural area of western Rajasthan, a cross-sectional study of 625 adolescent girls aged 11 to 19 years was carried out. Participants completed a questionnaire that included sociodemographic, clinical, and knowledge questions about anemia and its related factors. An HemoCue was used for hemoglobin analysis and anemia diagnosis. Results: Anemia was found in 56.32% ( n = 352) of the recruited population, with a mean of 9.92 (SD = 1.40). Mild, moderate, and severe anemia were found in 29.12%, 22.24%, and 4.96% of the participants, respectively. Girls aged 11 to 14 (AOR = 3.63, 95% CI: 1.76–6.38, P value = 0.042) and those with lower socioeconomic status (AOR = 4.37, 95% CI: 1.39–8.25, P value = 0.022) were more likely to have anemia than those of older age and higher socioeconomic status. Anemia was less prevalent in only one child/no siblings (AOR = 0.36, 95% CI: 0.16–0.73, P value = 0.041), and more prevalent in girls having less than 21 days of menstruation cycle (AOR = 5.37, 95% CI: 2.38–9.63, P value = 0.013), and 21 to 25 days of menstruation cycle (AOR = 3.81, 95% CI: 1.27–5.94, P value = 0.027). A total of 39.84% stated that anemia was caused by iron deficiency, followed by improper diet (32.64%). Furthermore, 56.32% agreed that the most common symptoms of anemia were weakness, and 51.36% of girls were told that anemia was treated with iron supplementation and a balanced diet (39.68%). Green leafy vegetables were considered a good source of iron by 56.48%, and 53.28% were educated about anemia by a teacher, followed by books (45.44%) and media (43.36%). Conclusion: The study shows high prevalence of anemia among adolescent females in the remote area of western Rajasthan. To improve girls health, it is necessary to increase their knowledge, attitudes, and practices in this area. Educational intervention and routine health check-up would be excellent ways to accomplish this.