Usability is widely recognized as a desired attribute of technology, referring to how usable it is to the intended users. As health information systems in developing countries are increasingly digitalized, interaction with familiar analog technologies is replaced by digital user interfaces for many health workers. An array of literature documents usability problems in such initiatives, arguing for their adverse effects on the users, and the system as a whole. What makes it challenging to achieve usability in this context has, however, not been explored extensively. This empirical paper attempts to bring focus to this gap, by defining the concept of usability design obstacles, which refer to aspects that complicate the usability design process. The relevance of the concept is illustrated through three empirical vignettes based on two action research projects in Uganda and India. Three concrete obstacles are outlined. These are (1) constraints introduced by software, (2) constraints introduced by legacy design, and (3) scale and heterogeneity of user groups. It is argued that to address the usability problems commonly outlined and discussed by existing literature, more focus on how to overcome such usability design obstacles is crucial. The obstacles identified in the empirical case of this paper also represent avenues for further research, which are discussed.