Available literature regarding the relations between attention, emotion understanding, and social competence is limited in its utility given discrepancies in construct definitions and measurement. The current study examined the relations between attention, as defined from a temperament perspective, emotion understanding, and social competence in preschool children, emphasizing specificity in the conceptualization and assessment of constructs. Attention was measured via the Structured Temperament Interview (STI) and the Childhood Behavior Questionnaire (CBQ), parent-report measures. Emotion understanding was assessed with the Emotion Comprehension Test (ECT), a performance assessment. The ECT differentiated between a child's ability to identify emotions in others based on facial expressions, situational cues, and behavioral cues. Social competence was measured via teacher ratings on the Social Competence Behavior Evaluation questionnaire (SCBE). Exploratory factor analyses of the STI revealed a two factor solution, including factors Low Distraction from Task, High Duration of Attention and Low Distraction from Emotional Investment. The former demonstrated multiple relations with the Effortful Control factor of the CBQ in correlational analyses, whereas the latter demonstrated multiple relations with the Negative Affect factor. Quantitative data, as well as qualitative analyses of themes emerging from parents' narrative STI responses, indicated that the STI encompasses both self-regulatory and reactive dimensions of attention, as well as features of emotionality and interest. Correlational and hierarchical regression analyses indicated that dimensions of attention including distractibility, attention span/persistence, and attentional focusing are related to a child's ability to identify emotions in others based on situational cues. Self-regulatory and reactive dimensions of attention, as assessed via the CBQ, demonstrated relationships with social competence outcomes, though no relations were evident between STI factors and SCBE scales. Ultimately, though dimensions of attention demonstrated relations with facets of both emotion understanding and social competence, in no case were dimensions of both attention and emotion understanding related to the same facet of social competence.