There is much research conducted on training teachers to use the evidence-based teaching strategies known as system of least prompts. However, there is little research conducted on using a modified system of least prompt. This study examined the fidelity of implementation by two early childhood teachers using a modified system of least prompts with preschool aged children. A multiple-probe design across participants was used to determine the effect of fidelity of implementation of a modified system of least prompts strategy on the level of on-task student engagement. The results showed that early childhood teachers could implement the modified teaching strategy with fidelity while also increasing the level of on-task engagement.