Context Developers' productivity plays an important role in software development organizations; however, in many cases the management of such human capital is mainly based on how project managers perceive productivity. Therefore, it is important to investigate what these perceptions are in practice. Goal This study's main goal is to understand project managers' perception regarding developers' productivity. Method We employed a qualitative research methodology using semi-structured interviews for data collection. We interviewed 12 managers from three software development organizations in the city of Manaus (Brazil). Results We identified that the managers' perceptions about developers' productivity are influenced by four different factors: (1) tasks delivered on time, (2) produced artifacts that do not need rework, (3) products that meet stakeholders' expectations, and (4) personal behavior such as focus and proactivity. Conclusions This qualitative study shows a perception of developers' productivity different from that presented in other research papers, and suggests that human factors play an important role in managers' perceptions about productivity. Future work will investigate how these perceptions concretely influence developers' productivity, and how they relate to the existing developers' productivity factors in the literature.