Right heart thrombus (RHT) is a life-threatening diagnosis that is rarely made in the emergency department (ED), but with the increasing use of focused cardiac ultrasound (FocUS), more of these cases may be identified in a timely fashion. We present a case of an ill-appearing patient who had an immediate change in management due to the visualization of RHT soon after arrival to the ED. The diagnosis was confirmed after a cardiology-performed ultrasound (US). This case illustrates the value of the recognition of RHT on FocUS and how US protocols designed for the evaluation of shock and shortness of breath may potentially be expanded to patients in a ‘compensated’ or ‘pre-shock’ state to expedite the correct diagnosis and to facilitate more timely management.Electronic supplementary materialThe online version of this article (doi:10.1186/s13089-015-0023-7) contains supplementary material, which is available to authorized users.