This mixed methods study reports on the perspectives of 143 preservice early childhood educators (ECE) and 208 elementary teacher candidates (TC) on teaching children with developmental disabilities and delays (DDD) in inclusive classrooms. A questionnaire was administered which included items on demographic characteristics, experience, knowledge, and feelings of competence when collaborating with colleagues and meeting the needs of students with DDD. Included was the Teachers' Sense of Efficacy Scale short form (Tschannen-Moran & Woolfolk Hoy, 2001). Qualitative data were collected through open-ended questions about successes and challenges in including children with DDD. Whenever applicable, items asked respondents to respond based on their most recent practicum in a child care or school setting. Similar findings were reported by both preservice ECE and elementary teacher candidates. TCs reported significantly greater experience, knowledge, and sense of efficacy in their teaching compared to ECEs, but no differences in feelings of competence. Analyses of open-ended questions about successes and challenges experienced by ECEs and TCs yielded similar themes related to differentiating teaching, enhancing participation for children, and collaborating, with TCs also expressing concerns about differentiating curriculum. Implications for early childhood and elementary teacher preparation programs are discussed.