The Language ENvironment Analysis (LENA) system has been used increasingly in research to record and evaluate the everyday speech of autistic children and their families. However, it is unclear how researchers are using LENA and whether the system is well-suited for work with autistic individuals. The purpose of this systematic review is to summarize the use of LENA in autism research, to highlight the strengths and limitations of the system as identified by researchers, and to provide recommendations for future research and clinical use. Forty-two studies that used LENA with samples of autistic children were identified through a systematic database search. Researchers using LENA in autism did so across a variety of ages, settings, and analytical approaches. Most studies used LENA within recommended guidelines. The most common purpose of using LENA was for exploratory research. Noted strengths of the LENA system included ecological validity, cost-effectiveness, and timely clinical feedback. Limitations included lower rates of speaker identification compared to human coders and limited information regarding speech context and language development. This systematic review provides key insights into the methods surrounding LENA use in autism research and serves to inform researchers and clinicians on best practices for future use with this technology. Lay abstract In research, language ability has historically been measured using structured tasks in laboratory settings. In recent years, there has been a growing emphasis on the need to instead capture language ability in an individual’s natural setting (i.e. through social interaction or in their home). Considering natural language may be particularly important for the autistic population, as an autistic child’s language ability can be very different depending on the setting. One common tool for capturing natural language is the LENA recording system, which takes audio recordings over long periods of time and provides estimates of children’s and caregivers’ speech. The purpose of this systematic review is to summarize the use of LENA in autism research, to highlight the strengths and limitations of the system as identified by researchers, and to provide recommendations for future research and clinical use. We identified 42 autism studies that used LENA in a variety of ways and settings. Most studies used LENA within the guidelines put forth by its creators, and it was most commonly used to understand speech or speech development for autistic children. LENA is a useful tool for clinicians and caregivers to gain some insights into child speech, but those considering using it should be aware of concerns about its accuracy and limitations about the information it provides. In this review, we supplement the official LENA guidelines with specific suggestions for use with the autistic population.