Despite a wealth of effective psychotherapies for youth mental health disorders, a significant proportion of affected youth do not receive treatment (Merikengas et al., 2011). Although a variety of factors may contribute to this treatment gap, one proposed hypothesis is a lack of caregiver mental health literacy. Mental health literacy (MHL) is defined as the “knowledge and attitudes about mental disorders that aid their recognition and treatment” (Jorm, 2000). Mental health literacy is a relatively new construct, and therefore, there are few psychometrically validated measurement tools available. Furthermore, no validated measures have been developed specifically to assess knowledge about youth mental health problems, and few studies have focused on measurement of caregiver MHL in Latinx samples. Additionally, although some emerging literature focuses on interventions to improve mental health literacy for specific populations, there are no interventions to date that specifically meet the needs of caregivers in Latinx communities, where negative attitudes about mental health problems and treatment is high but service utilization is low (Alegr�a, Vallas, & Pumariega, 2010; Turner et al., 2015). Using a mixed-methods approach, the goals of this dissertation were to: 1) develop an objective measure of MHL that specifically assesses youth mental health problems; 2) validate this measure in a caregiver sample, with a particular focus on Latinx caregivers; 3) examine the relationship between MHL and related constructs, including stigma toward having a child with mental illness and attitudes about seeking treatment for a child with mental health problems in this sample; and 4) explore preferences for and acceptability of interventions to improve caregiver MHL in Latinx communities. Study 1 described the initial development and validation for a newly developed mental health literacy test (MHLT v1). The MHLT v1 consisted of 40 statements that were presented in a True/False/Unsure format and assessed knowledge specifically about youth mental health problems. This measure was piloted in an undergraduate sample (N=354) and results demonstrated that the MHLT v1 had acceptable internal consistency and strong construct validity. Study 2 built upon these findings and discussed the refinement of the MHLT and psychometric validation of this measure in a caregiver sample. One-hundred and sixty-nine caregivers completed the revised MHLT (v2), along with two measures of attitudes about having a child with mental illness and seeking professional help for child’s mental health needs. Demographic variables of interest (e.g., race/ethnicity, education, income), history of mental health diagnoses and service use, and most helpful and trusted information sources, were also collected. Results demonstrated that the MHLT v2 demonstrated good internal consistency. Across demographic variables, non-Latinx White participants outperformed Latinx participants, and participants with graduate education scored higher than participants with a bachelor’s degrees or less. Scores on the MHLT were negatively correlated with stigma about having a child with mental illness, but not significantly correlated with stigma about help-seeking. In Study 3, ten Latinx caregivers participated in a one-time, individual interview and provided feedback about the MHLT content and test-taking experience. Participants reported that the MHLT was manageable and provided suggestions to refine item content. Additionally, interviews explored caregivers’ perceptions about their own knowledge of children’s mental health problems, stigma, and attitudes about help-seeking. Participants in this sample reported low levels of stigma and high openness to seeking professional help for their children’s mental health needs. Finally, participants discussed the perceived helpfulness and feasibility of interventions to improve caregiver mental health literacy, and provided input to improve the acceptability and effectiveness of knowledge interventions for Latinx caregivers in their community. All participants reported that increasing caregiver MHL was important and/or would be helpful or useful. However, participants were mixed about how other community members would respond to programs. Suggestions to increase community engagement and acceptability included delivery by a mental health professional, offering programs in Spanish and English, and reducing use of stigmatizing language (e.g., mental illness) in program content and advertisements.