Preservice teachers' roles in conducting online learning (OL) are getting more attention since OL is increasingly used as instructional methods. Acknowledging the level of efficacy in teaching mathematics through online learning can provide more inputs for developing OL skills. Hence, this study aims to identify the level of efficacy and motivation in teaching mathematics through online learning. A correlational research design was employed to collect quantitative data. A questionnaire was adapted from two instruments, and it was distributed to 126 preservice mathematics teachers. The samples were selected using convenient sampling techniques with consideration of easy access to their agreement to participate in the study. The data was analysed using both descriptive and inferential methods such as Pearson Correlation. The findings demonstrated that the preservice teachers were highly effective and motivated in their instruction of mathematics via online learning. Additionally, a mildly favourable association between preservice teachers' efficacy and motivation in a mathematics class was also found in the data. Although OL is not frequently used by preservice teachers, this study found that preservice teachers demonstrated favourable reactions in terms of motivation and instructional efficacy. However, it is recommended that future studies should investigate the use of qualitative research methodologies to gather insightful data and thereby deliver more comprehensive conclusions.