Since the start of the COVID-19 pandemic, tele-based methods of autism assessment have been relied upon to a previously unparalleled degree; however, the need for such advancements is not new. Observation-based measures are a crucial component of face-to-face autism diagnostic evaluations, but few validated observation tools exist for remotely assessing autism across childhood, particularly for older children and adolescents, providing minimal guidance in this arena. Sanchez and Constantino (2020) previously validated a brief, face-to-face, clinician-facilitated observation coded according to the Childhood Autism Rating Scale, Second Edition (CARS-2). During the pandemic, this measure was adapted as a remote observation (rCARS2 Observation), but has yet to be validated in this format. The current study validated the rCARS2 Observation against the "gold-standard," in-person Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). In this sample of 30 children ages 1.97 to 16.66 years (M = 7.35, SD = 4.00), ADOS-2 and rCARS2 Observation total scores were highly correlated (ρ = .644, p < .001). Receiver operating characteristic (ROC) curves optimized rCARS2 Observation cutoff scores to maximize sensitivity and specificity in predicting possible diagnostic classification (88.9% sensitivity, 80% specificity) and ADOS-2 classification (83.3% sensitivity, 70.6%, specificity). At optimal cutoffs, the rCARS2 Observation predicted the correct diagnosis in 82.8% of cases and the same classification as the ADOS-2 in 75.9% of cases. Validation of this instrument provides support for an accessible and efficient remote autism observation. This is crucial in ensuring uniform training and clinical procedures for tele-assessment of autism, to help mitigate long-standing barriers to service access (e.g., geography, cost, availability). / Doctor of Philosophy / During the COVID-19 pandemic, many in-person services, including assessments for an autism diagnosis, were forced to shift to telehealth. When an autism assessment is completed in-person, it requires an "observation-based" measure, meaning that a clinician directly observes a child's behavior, in addition to an interview with a parent or caregiver. Families have faced barriers to accessing in-person autism assessments even prior to the pandemic, including geography, transportation difficulties, shortage of autism-specific providers, and high cost of services. As such, tele-assessment of autism is an important tool to consider in helping families to access these services. However, observation-based autism assessment measures that can be completed through telehealth from families' homes are few and not well-understood. The current study explores a brief telehealth observation tool (the rCARS2 Observation) and compares it to the "gold-standard" autism observation-based tool (the ADOS-2) that is typically used during in-person assessments of autism. This study found that scores on this remote measure and the in-person measure were strongly related and the remote observation measure showed great promise for predicting a diagnosis of autism in this study. This is the first study to explore the rCARS2 Observation to understand how well it can evaluate children's autism characteristics from home as compared with an in-person assessment tool. The success of this remote observation measure in the current study is promising and suggests that this may be one remote tool that clinicians can use in combination with a parent- or caregiver-interview to evaluate a child for an autism diagnosis as a shorter and more accessible tool to overcome many barriers to accessing services.