Parent-teacher relationship (PTR) quality is linked to child and family-school functioning and may be especially important in the school adjustment of autistic children. However, measurement of PTR quality has been limited by inconsistency in the use of measures, a paucity of two-informant measurement, and limited psychometric consideration. We examined the psychometric properties of the Parent-Teacher Relationship Quality Scale (PTRQS), a parent- and teacher-report measure of PTR quality derived from multiple sources. Specifically, we examined the factor structure, reliability, and convergent validity of the PTRQS among parents and teachers of 192 autistic children in preschool to 2nd grade. Results supported a three-factor model, including (1) parent-perceived relationship quality, (2) teacher-perceived comfort with parent(s), and (3) teacher perceptions of parent abilities. Scores exhibited high internal consistency. As evidence of convergent validity, all three factors of PTR quality, as well as the total PTRQS score, were strongly associated with parent interview-based PTR quality, parent perceptions of teacher effectiveness, and teacher-rated parental school involvement. The two teacher-rated PTR quality factors were also associated with student-teacher relationship quality. Results indicated that (1) the measure can validly capture PTR quality in the context of preschool and early elementary-age autistic children; (2) early PTR quality is linked to parental involvement; and (3) teacher-rated PTR factors are linked to autistic students' own relationships with their teachers. The results have implications for researchers and school psychologists measuring PTR quality in their practice. [This paper was published in "Journal of School Psychology" v95 p25-42 2022 (ISSN 0022-4405).]