Student outcomes depend on the implementation of intervention practice elements, which are the specific behaviors that front-line implementers deliver as part of their direct interactions with students. Tier 1 PBIS is a well established practice in schools but existing guidance on practice elements is often conflated with guidance on organizational systems that support implementation. The goal of this study was to distill the specific practice elements of Tier 1 PBIS from the established core features using an expert consensus process. A panel of nine Tier 1 PBIS research and practice experts participated in three iterative rounds of information gathering and feedback within an electronic Delphi study that structured the consensus-building process. The expert panel reached consensus by distilling Tier 1 PBIS into 16 distinct practice elements organized into five thematic domains. The thematic domains from the present study align with existing literature on core Tier 1 PBIS features but the practices in each domain clearly define the specific, expected actions of frontline implementers. Implications are discussed in terms of how the identified practice elements may be used to inform intervention fidelity monitoring and targeted implementation supports for front-line implementers.