Heritage language (HL) schools are helping ethnic groups pass to their children their cherished heritage languages (HLs), values, traditions, and a sense of cultural belonging. The number of successfully operated HL schools is growing across the United States. However, the factors that are paramount to the successful operation of these schools have been overlooked and received little scholarly attention for empirical research. The purpose of this study was to explore the factors vital for the successful operation of HL schools from the perspectives of the stakeholders of those schools. The study used a sequential explanatory mixed-method design in which quantitative data in the form of a survey was collected first, and qualitative data from interviews was amassed to help explain the quantitative results. The quantitative data were collected from several groups selected from 3 HL schools representing 3 different ethnic groups. These groups included principals (N = 3), teachers (N = 24), parents (N = 107), and students over 12 years of age (N = 84). Four sets of parallel survey questionnaires were used to collect data from each of these groups, and the data were analyzed using descriptive statistics. The qualitative data were obtained through follow-up interviews with principals (N = 3), a school board member (N = 1), and students ages 6 to 12 years (N = 18). Three sets of open-ended interview questions were employed to collect data from the respective groups of interviewees. This study found that strong parent involvement, high quality of teaching, stable financial sources, and effective extra-curricular activities were the central pillars of the HI, schools' operational successes. The quantitative part of the study showed that participating groups across the HL schools had mixed preferences when prioritizing the 4 factors. However, the themes that emerged from the analysis of the qualitative data emphasized that successful HL schools are built upon integrally connected factors.