Annual reports are a central element of international bureaucracies' accountability communication to member states and other stakeholders. Most UN system bureaucracies produce reports of significant length and detail. International agencies use these reports to draw attention to particular challenges or successes. Hitting the right tone with their diverse stakeholders is crucial to maintain continued support. UN agencies do so by employing differentiated sentiment-loaded language alongside factual reporting. We argue that agencies' operational focus, administrative structures and resource mobilization needs have a significant impact on how they use sentiment to communicate with different stakeholder groups. Drawing on a dictionary-based sentiment analysis of three text corpora of annual reports produced by three UN system agencies—UNRWA (reports published from 1951 to 2019), UNHCR (1953–2019) and IOM (2000–2019)—we show a general trend toward increased positive sentiment use across all three agencies, coinciding with a period of stronger donor orientation. At the same time, we find a more volatile and agency-specific use of negative sentiment in response to field-level challenges that are communicated to stakeholders in line with agencies' evolving mandates. Through a text-as-data perspective, this contribution enhances our comparative understanding of the diverse and context-dependent language of international bureaucracies. Points for practitioners Reading UN agency reporting, practitioners need to be aware of the constraints and incentives that international bureaucrats face—notably operational focus, administrative structures and resource needs—that drive tone differences across reports and over time.