This article investigates the extent to which young people are able to comprehend the political messages contained in satirical videos that circulate online. We do so through an analysis of responses to videos embedded within an online survey of 15- to 25-year-olds (N = 2070) conducted in 2011. Respondents were randomly assigned to view one of two short, humorous YouTube videos relating to immigration policy and were then asked questions that tested their comprehension of what they had seen. Substantial proportions of our sample were unable to answer these correctly. Further analysis indicates that individuals’ levels of political knowledge and their predisposition to agree with the message contained in the video are strong predictors of comprehension. These findings indicate that the potential impact of incidental exposure to online political communications is smaller than many scholars have assumed, particularly when the message is inconsistent with the viewer’s prior beliefs.