This research explores how paper and online assessments (OA) can affect EFL learners' personal development variables such as self-esteem, mindfulness, demotivation, and language learning development. Sixty intermediate English as a foreign language (EFL) students participated in the current research and were randomly grouped into the experimental group (EG) and the control group (CG). Before the intervention, the data collection tools assessing language learners' self-esteem, mindfulness, demotivation, and language learning development were administered as pre-tests to all the participants. Subsequently, the EG was taught all lessons of the coursebook, Top Notch 2, by utilizing OA while the CG was taught the identical lessons using a conventional (pen and paper) assessment. In the post-treatment phase, the two groups completed the post-tests on self-esteem mindfulness, demotivation, and language learning progress. The study demonstrated that the EG group outperformed the CG group on the four post-tests. The findings indicate that the intervention of OA significantly enhanced language learning outcomes and psychological well-being regarding the measured personal development variables. The enhanced efficacy in the EG group can be ascribed to the utilization of OA during the treatment phase, which has a beneficial effect on academic and personal development. This study also posits that integrating OA augments psychological engagement and language development among EFL learners. It highlights the implications of the results associating teaching EFL via OA with the observed personal development aspects and attributes them to effects of positive psychology.