Autism is described as a lifelong neurodevelopmental spectrum condition, with each individual varying in their abilities across social and cognitive domains. The current prevalence estimates range between 1/100 and 1/132 worldwide. Autism is characterized by a complex collection of manifestations, with repetitive behaviors, social communication difficulties, and sensory hypersensitivity and hyposensitivity. There is evidence to suggest that certain executive function (EF) skills (a group of important thinking skills that allow individuals to set and complete goals) are impaired in autistic children. These include interference control (the ability to resist distracting information), flexible switching (the ability to switch between thoughts and adapt behaviour according to a changing environment) and sustained attention (the ability to focus over a period of time). Furthermore, impairments in these EF domains have been evidenced to underlie some of the key characteristics of autism and negatively impact quality of life. There is also evidence to suggest that knowledge of two languages (i.e., bilingualism; a skill shared by more than half of the world's population, comprising an extensive spectrum of language experiences and markers) has the potential to ameliorate these EF domains. This evidence is surrounded by debate, however, with evidence for and against a bilingual advantage. Nevertheless, bilingual disadvantages in EF domains are rarely, if ever, in evidence. Despite this, there are parent and practitioner concerns with respect to raising autistic children speaking more than one language. This raises the question: what kind of impact does bilingualism have on the EF abilities of autistic children? Could bilingualism mitigate potential EF difficulties in autistic children? Well, only a handful of studies worldwide have explored this question, all of which strongly support the idea that bilingualism is not harmful to autistic children's EF development, and may even confer some advantages. Nevertheless, our understanding of the EF profiles of bilingual autistic children remains very limited. Given the rising diagnostic rates of autism and increases in the worldwide bilingual population, it is imperative to chart the effects of bilingualism on autism, especially in a domain evidenced to impact quality of life like EF. This doctoral research explores the effects of bilingualism on a group of EF skills selected based on their theoretical relevance to bilingualism (i.e., the Adaptive Control Hypothesis) and autism (the Executive Dysfunction Theory). All data were collected in the United Arab Emirates, a country that offers a predominantly dual-language switching environment (i.e., using two languages in the same context), which is also of theoretical relevance to bilingualism. Using directly-assessed, experimental measures of EF, findings from the first investigation (Chapter 3) with 93 participants (autistic and typically developing), revealed an advantage for bilingual autistic children on one outcome measure of sustained attention and equivalent performance to monolingual autistic children on all other EF outcome measures. The findings from this investigation, however, reflect EF performance using laboratory-type tasks, assessed at one point in time. This is at best, a partial picture of EF, bilingualism and autism. Therefore, I then asked, what is the impact of bilingualism on EF if the measures deployed capture a wider time span and everyday types of situations? To address this knowledge gap, I launched the second investigation (Chapter 4) with 80 participants (autistic and typically developing) using informant-report measures of EF, capturing both parent and teacher perspectives on children's abilities. The first key finding is that parent-reported EF revealed an advantage for bilingual autistic children on all EF domains, relative to monolingual autistic peers. The second key finding is that second language proficiency predicted parent-reported sustained attention, and second language current exposure predicted parent-reported interference control. The third key finding is that poorer parent-reported EF abilities were associated with more clinically significant features of autism. Given the known heterogeneity between autistic children, my third and final investigation (Chapter 5) went on to examine variability in my data in more detail, using a multiple case series approach to analyse EF data from 27 autistic participants. The first key finding was that the individual experience of autism seemed to shape EF capabilities. To illustrate, in contrast to group-level findings (Chapters 3 and 4) which framed autistic group performance as 'impaired', a multiple case series analysis showed that the majority of autistic participants performed equivalently to typically developing peers. The second key finding is that I found no support for 'spiky' autistic EF profiles (i.e., one that has a mix of enhanced, impaired, and average performance). The third key finding was that more strengths were revealed on directly-assessed EF than parent-reported EF, which was, in turn, more positive than teacher-reported EF. To my knowledge, this is the first investigation at this interface to use a multidimensional EF approach - EF was assessed via a combination of direct and informant-based (parent and teacher reports) measures - and to employ mixed analytic methods (i.e., group and multiple case series analysis). Further new contributions come from the inclusion of sustained attention as a relevant domain of interest. Additionally, this work contributes to the diversification of autism research samples beyond WEIRD (western, educated, industrial, rich, and democratic) samples. Finally, this work contributes new findings from the targeted investigation of the Adaptive Control Hypothesis theoretical model in a non-typical population. In the final chapter (Chapter 6), the overall findings of the study are discussed, to draw conclusions, identify evidence-based implications for families, practitioners, researchers, and chart new areas of bilingualism research in childhood autism.