Improving autism spectrum disorder screening and referral in primary care may reduce autism spectrum disorder disparities for Latino children. The REAL-START intervention aimed to increase primary care provider adherence to autism spectrum disorder and developmental screening guidelines, and to increase Early Intervention referral for children at developmental risk in primary care clinics serving Latinos. This quasi-experimental study enrolled six Oregon primary care clinics. Clinic staff attended one initial and three follow-up trainings. Trainings addressed screening, billing, referral, and follow-up issues specific to Latinos. Clinic leaders met with a quality improvement facilitator to review performance. Medical record review measured screening and referral at 18- and 24-month well-child visits at baseline and 3, 6, 9, and 12 months. State Early Intervention database queries assessed Early Intervention eligibility. Overall, 2224 well-child visits were assessed (39% Latino). Clinics improved rates of autism spectrum disorder screening from 70% to 94% and general developmental screening from 62% to 95%. Adherence to screening guidelines increased from 46% to 91%. Proportion of children referred to Early Intervention was unchanged, but total referrals increased and age range of referred children broadened. Time to Early Intervention evaluation was slightly shorter among screening-age children. REAL-START may improve screening and referral for autism spectrum disorder and developmental delay in Latino communities.