Background <p>Alexithymia inhibits one’s ability to respond to emotional stimuli and may diminish emotion regulation attempts resulting in greater internalizing psychopathology. However, most literature has focused on <i>intrapersonal</i> emotion regulation (ER) in the context of alexithymia and internalizing psychopathology. We examined the main and interaction effects of alexithymia features and two <i>interpersonal</i> ER strategies on internalizing psychopathology.</p> Method <p>Two samples (<i>N</i> = 986 &amp; <i>N</i> = 181; <i>M</i>_ages = 36.36 [12.09] &amp; 20.01 [2.18]) were recruited through Amazon MTurk and a large northeastern university for two studies evaluating an interpersonal ER measure and examining ER and risky behavior. Participants completed self-report measures of interpersonal ER, alexithymia features, and internalizing psychopathology. Hierarchical linear regressions were used to examine the main and interaction effects of alexithymia features and interpersonal ER on internalizing psychopathology.</p> Results <p>There were no significant main or interaction effects for venting on internalizing psychopathology after controlling for sex and alexithymia features. However, there were significant main and interaction effects for reassurance-seeking, such that at high levels of alexithymia features, the association between reassurance-seeking and internalizing psychopathology was positive and stronger in both samples.</p> Conclusions <p>Our study highlights the interdependent effects of alexithymia features and interpersonal ER on internalizing psychopathology. Clinical implications are discussed.</p>