The main goals of this dissertation are to investigate the associations between language and executive functions, including selective auditory attention, in Swedish children aged 4–6, to examine possible links to factors relating to the child and his/her social environment, and to evaluate preschool interventions with regard to potential improvements in language and/or executive functions. Measures were obtained by combining results from behavioral tests, language samples in the form of narratives, parent and teacher ratings and a measure of selective auditory attention as brain activity. Additionally, previous work regarding the nature and direction of the association between language and executive functions is reviewed and discussed. Progress during preschool years in language and executive functioning development seem to go hand in hand, and a body of work has indicated that language and executive functions are closely associated, although directions of potential casual relationships are still unclear. For Swedish, preschool-aged children, little is known of the language–executive functions relationship and the extent to which these skills can be improved via pedagogical working methods or interventions. The first paper investigates the language–executive functions relationship and potential associations to background factors, and the second paper examines the same research questions in larger sample, adding a selective auditory attention measure. The third paper constitutes one of the first randomized controlled trials in the Swedish preschool context and investigates effects of two contrasting pedagogical interventions compared to business-as-usual. The fourth paper explores links between children’s spontaneous explanations of a fictional misunderstanding, their language skills and their executive functions. In line with previous work from other contexts, results confirm an association between children’s grammar skills and inhibition, including selective auditory attention. Children’s socioeconomic background is significantly related to language skills, executive functions and selective attention. The current results also suggest a female advantage for receptive vocabulary and morphosyntax and indicate that bi- and multilingual children perform lower than monolingual peers with regard to receptive vocabulary in the majority language, also when controlling for socioeconomic status. The preschool interventions did not lead to any gains in language, executive functions or selective attention compared to the control group. Further work is clearly needed to provide a solid evidence-base for Swedish preschool practices. Future studies should focus on identifying relevant mechanisms in order to enable early intervention targeting children at risk for lagging behind their peers already in preschool. Previous empirical work as well as theoretical suggestions regarding the nature and direction of the links between language and executive functions are divergent, which is related to a lack of consensus with regard to underlying theories and to problems with definitions and assessment. In this thesis, it is suggested that the association is intertwined and reciprocal, congruent with a view on development as dynamic and complex and in line with a theory of mutualism. Future work is needed to refine theories and to formulate testable hypotheses regarding the language–executive functions relationship.