In this paper, we examine how referees establish interpersonal relationships by mitigating criticism and expressing compliments as a realization of politeness strategies through the analysis of a specific corpus of transparent peer review reports (TPRs) with 220 reports totaling approximately 200,000 words. For the analysis, employing a framework drawn primarily on Brown and Levinson’s (1987) politeness strategies and following a detailed review of the literature, we coded all occurrences of politeness strategies using UAM Corpus Tool 3.3x (O’Donnell, 2021). Conducting intercoder/intracoder reliability tests, we identified and interpreted a variety of politeness strategies at the sentence and discourse levels, which were used for mitigating criticism and expressing compliments. Our results suggest that reviewers resorted to a variety of politeness strategies, predominantly negative politeness strategies, to mitigate their criticism directed at the authors of manuscripts. This is significant especially in the light of earlier studies where reviewer reports appeared to include some blunt/hurtful comments due partly to the anonymity of the reviewing process. Rather than focusing on just communicating criticism or a required change, reviewers were found to have cared about politeness and seemed to achieve interpersonal communication goals in TPRs by means of favoring an egalitarian approach rather than an authoritative one, supporting Gosden’s (2003) argument on the interpersonal aspect of reviewing discourse. This research contributes to our understanding of how criticism in TPRs can be conveyed without imposing, leading to encouraging, constructive and polite reports in English as part of science communication, especially when the review reports are publicly available.