two hundred single post-secondary 世界杯2022赛程表淘汰赛 participated in a longitudinal study including online, laboratory, and speed dating components. this methodology was used to examine the link between romantic relationship formation and the heart, specifically heart rate variability. relationship success was operationally defined as matching during a speed dating session or forming a romantic relationship over a prospective 6-month period. both hrv reactivity and resting hrv were related to relationship success, each through different mechanisms. in a moderated mediation model, higher hrv reactivity predicted greater use of the emotion regulation strategy of reappraisal which, in turn, interacted with body mass index (bmi) to predict relationship success. higher use of reappraisal increased relationship success amongst higher-bmi individuals, but hindered relationship success amongst lower-bmi individuals. in a separate moderation model, a pattern of increasing hrv in response to a stressor conferred an advantage in relationship success only to participants with lower resting hrv. finally, resting hrv was found to predict relationship success through the mediator of mate value. higher resting hrv was associated with higher mate value, which predicted higher subsequent matching and relationship formation. these results are discussed in the context of the generalized unsafety theory of stress. this investigation of human relationship formation through a biological lens provides insights into how otherwise imperceptible cardiac experiences are contributory to romantic relationship formation.