Loneliness is connected to poorer health outcomes with stress reactivity proposed as an underlying mechanism. The present study explored whether the relationship between loneliness and cardiovascular reactivity (CVR) varies across acute psychological stress tasks. Eighty-eight healthy younger adults completed a psychometric measure of loneliness and participated in a standardised cardiovascular stress-testing protocol, with a public speaking and a mental arithmetic task. Cardiovascular functioning was assessed before and during the acute stress exposure. Higher levels of loneliness significantly predicted lower total peripheral resistance (TPR) reactivity to the public speaking task but not to the arithmetic challenge. This suggests that the effect of loneliness on cardiovascular reactivity to acute stress may vary by stressor type. These findings are discussed in relation to future research.