The main purpose of this article is to show that the Ka’apor language exhibits both direct object marking (DOM) and differential subject marking (DSM). This research demonstrates that the particle ke is responsible for triggering these systems, since it is used when agent subjects are semantically affected by the event described by the verb and when objects are high on the animacy scale. In this sense, the DOM mechanism in Ka’apor is regulated by both the animacy and definiteness scales. With regard to DSM, I hypothesize that it emerges as an example of a markedness reversal, since affectedness is not a typical property of subjects, but only of objects. As a result, DSM in Ka’apor is characterized by the fact that only subjects which resemble typical patient objects are overtly case-marked by the particle ke.