<p>Self and peer assessment in group work offers numerous benefits but is also susceptible to bias. Yet, research examining bias in self and peer assessments often overlooks cultural perspectives and predominantly favors Western contexts. This study aims to address this gap by examining how culture influences rater bias in self and peer assessments conducted in the context of group work within an Indonesian setting. This qualitative study, guided by a cultural psychology framework, uses focus group data to explore the mechanisms, causes, and implications of rater bias in assessment practices. Findings indicate that students exhibit modesty in self-assessment and leniency toward friends, driven by a need to align with expectations and preserve relationships. Students avoid confronting underperforming peers, using the assessment rubric as a discreet channel to communicate with lecturers. The study concludes with practical implications for assessment practices.</p>