The COVID-19 pandemic has radically altered everyday interactions, potentially disrupting the process of romantic relationship formation. Prior research suggests that threats to the basic psychological need for relatedness, along with negative mental imagery, can lead to an obsessive preoccupation with a romantic interest. The present research examines how the relatedness-threatening nature of the pandemic may similarly facilitate problematic relationship behaviors. Two studies—a small-scale natural experiment with measurements before and during the pandemic (Study 1) and a daily diary study (Study 2)—investigated how relatedness frustration and negative fantasies predict presumptuous romantic intentions. In Study 1 these threats unexpectedly corresponded to reduced presumptuous romantic intentions, though no such main effect was present in Study 2. Replicating prior experimental work, in both studies, more negative fantasies about a romantic target predicted greater presumptuous romantic intentions. Study 2 also revealed that at the between-person level the combinatory effect of relatedness frustration and negative fantasies led to greater intentions. At the within-person level, this combinatory effect led unexpectedly to reduced intentions. Finally, there was substantial heterogeneity in the within-person effect of COVID-induced relatedness frustration: although frustration stoked intentions for some individuals, for others it reduced intentions. This work suggests that for many, the early social ramifications of COVID-19 reduced motivation to presumptuously pursue romantic relationships. Yet, certain individuals, particularly those with more negative fantasies, are more prone to pursue presumptuously amidst the pandemic.