Background: Vulnerable people are at higher risk for ill health and often experience discrimination in health services. Persons with disabilities, People with Dementia (PWD), and People with HIV/AIDS (PLWHA) are some groups of people with vulnerabilities who often need hospital care. Nurses are the largest group of health personnel and frequently meet with these patients so that the attitude of nurses can have a consequence on the quality of health care. Research Objectives: To identify nurses' attitudes towards vulnerable people and factors related to their attitudes. Methods: This quantitative research used a cross-sectional design. The research subjects were 386 nurses in the main public Dr. Sardjito hospital selected using a convenience sampling technique. Data were collected in January-February 2021 with a Google Form. Researchers used a demographic data questionnaire, an attitude questionnaire (Attitude Toward Disabled Person Scale Form O, Dementia Attitude Scale, and AIDS Attitude Scale), and a knowledge questionnaire (Self-Administered Questionnaire about Knowledge), Dementia Knowledge Assessment Scale, and HIV-Knowledge Questionnaire-18). Data were analyzed using non-parametric statistical tests, specifically the Spearman rank, Mann-Whitney, and Kruskal-Wallis tests. Results: The score of nurses' attitudes towards persons with disabilities was 54.00 out of 120; the score of nurses' attitudes to PWD was 102.00 out of 140; and the score of nurses' attitudes toward PLWHA was -0.65 out of +5. Knowledge, history of interaction, and experience in caring have a significant effect on nurses' attitudes towards vulnerable people (p value <0.05). The education level only affects the attitudes of nurses towards persons with disabilities (p value = 0.042). Family history only affects nurses' attitudes to PWD (p value = 0.013). Age and special education/training only affect the attitudes of nurses on PWD and PLWHA (p value <0.05). Conclusion: Nurses tend to present positive attitudes toward PWD, but nurses are inclined to show negative attitudes against people with disabilities and PLWHA. Knowledge, caring experience, and interaction are confirmed to have an effect on nurses' attitudes with the result that programs to increase knowledge and experience of nurses towards vulnerable groups are recommended for this group. Keywords: Attitude, Dementia, Disability, HIV/AIDS, Knowledge, Nurse.