Empathy is an important socio-emotional process for interpersonal interactions, moral decision-making, and a functioning society as a whole. Emotional contagion is an unconscious process that forms the basis for empathy. While differences in levels of empathy have been reported in various clinical populations, these differences also exist in the general, non-clinical population. Two commonly-occurring personality traits, alexithymia and sensory processing sensitivity (SPS), have been linked to individual differences in empathy and its related constructs. The current study investigated the links between alexithymia and SPS, early adverse life experiences, mood, self-reported levels of empathy and related constructs, and emotional contagion induced in a behavioural task. 305 adult participants watched brief affective film clips chosen to induce positive, negative, mixed, and neutral emotional states, and rated how strongly each film made them feel various emotions. Participants also completed self-report measures of alexithymia, SPS, empathy and related constructs, childhood emotional abuse, and current mood. Alexithymia positively predicted the number of emotions experienced by participants during the behavioural task, as well as negatively predicted other-focused aspects of self-reported empathy, including perspective-taking and empathic concern. SPS positively predicted the strength of the emotions experienced by participants, the extent to which they felt their own emotions matched those of the main characters in the films, and both other-focused empathy and self-focused processes, such as experiencing feelings of personal distress or strong emotions in response to the films. The findings suggest that alexithymia reduces the other-focused component of empathy, potentially by providing mixed affective signals that are difficult for individuals to characterize. SPS, on the other hand, appears to increase both other- and self-focused empathy, potentially by increasing the strength and granularity of the individual’s emotional response.