Early detection methods for autism spectrum disorder (ASD) in infancy are rapidly advancing, yet the development of interventions for infants under two years with or at-risk for ASD remains limited. In order to guide research and practice, this paper systematically reviewed studies investigating interventions for infants under 24 months with or at-risk for ASD. Nine studies were identified and evaluated for: (a) participants, (b) intervention approach (c) experimental design, and (d) outcomes. Studies that collected parent measures reported positive findings for parent acceptability, satisfaction, and improvement in parent implementation of treatment. Infant gains in social-communicative and developmental skills were observed following intervention in most of the reviewed studies, while comparisons with treatment-as-usual control groups elucidate the need for further research. These studies highlight the feasibility of very early intervention and provide preliminary evidence that intervention for at-risk infants may be beneficial for infants and parents.