||Decades of research provides evidence that social relationships are powerful predictors of health and mortality. One important moderator of the link between relationships and health is relationship quality, with supportive relationships often attenuating, and ambivalent relationships amplifying, reactivity that can cause wear-and-tear on the cardiovascular system. While much work has examined self-report (explicit) attitudes regarding relationship quality and links to cardiovascular reactivity (CVR), no study to our knowledge has examined whether implicit attitudes have similar or different effects. The current study examined whether implicit friendship attitudes influenced cognitive appraisals and cardiovascular reactivity during a negative event discussion. Based on prior work, we predicted interacting with friends rated as either explicitly or implicitly supportive would reduce CVR, as well as increase perceptions of control, and decrease perceptions of threat and stress associated with the speaking task. However, when interacting with a friend rated as either explicitly or implicitly ambivalent, we predicted a pattern similar to what we have traditionally seen with explicitly-rated ambivalent ties to emerge, such that participants would experience increased CVR, lower perceptions of control, and higher perceptions of threat and stress associated with the speaking task. Results did not support these hypotheses and unexpectedly, demonstrated some effects opposite to what was anticipated based on prior work. We consider several study limitations that shed light on these unexpected results, as well as discuss cognitive organization theories that may be relevant in thinking about implicit friendship attitudes and possible links to health in future work.