Due to the COVID-19 pandemic, online learning has gained significant attention within the educational context of Vietnam. Nonetheless, there is a shared concern among educators about the effectiveness of the online platform that supports positive learning outcomes. To address this, the Connectivist Learning Environment (CLE), where learning activities were designed and aligned with connectivism theory, was introduced. This study explored whether or not the CLE helped develop the general pedagogical knowledge (GPK) of Vietnamese pre-service English teachers (PETs) and the possible factors that led to their GPK development. This study involved 40 pre-service English teachers at a university in Vietnam and 15 Vietnamese and foreign teachers of English. Data were collected through pre-tests, posttests, online reflective journals, an online survey, and a semi-structured interview. An independent paired sample t-test and repeated measures ANOVA were used to analyze quantitative data, while content analysis was used with qualitative data. The findings revealed that the GPK of pre-service English teachers is significantly higher after 9-weeks of participation. The participants stated that the CLE is a beneficial learning platform with various positive attributes. In addition to the theoretical and pedagogical implications, this study offers insights for future research studies.