The reliability of online mood manipulations is undermined by participants’ non-compliance behavior, e.g. skipping a part of the experiment or switching between web pages during the mood manipulation. The goal of the current research is to investigate (1) whether and how mood manipulations are threatened by non-compliance behavior, (2) whether it is confounded with the induced mood state as predicted by Affect Regulation Theory, and (3) what measures can be taken to control for this. In two online-experiments, non-compliance behavior was assessed during the mood manipulation with movie clips by tracking interruptions of watching and page switches. The results confirm the affect regulation hypothesis demonstrating that people confronted with a negative emotion content interrupted watching the video and switched between pages more often than people with a positive content. Methodologically, this causes a threat to the internal validity of internet-based mood manipulation studies. To decrease the risk of non-compliance, the current study recommends to block skipping a part of the mood manipulation, detect page focus events and measure the time people stay on a page.