BACKGROUND: With the paucity of high-quality studies on longitudinal basic critical care echocardiography (BCCE) training, expert opinion guidelines have guided BCCE competence educational standards and processes. However, existing guidelines lack precise detail due to methodological flaws during guideline development. RESEARCH QUESTIONS: To formulate methodologically robust guidelines on BCCE training using evidence and expert opinion, detailing specific criteria for every step, we conducted a modified Delphi process using the principles of the validated AGREE-II tool. Based on systematic reviews, the following domains were chosen: components of a longitudinal BCCE curriculum; pass-grade criteria for image-acquisition and image-interpretation; and formative/summative assessment and final competence processes. STUDY DESIGN AND METHODS: Between April 2020 and May 2021, a total of 21 BCCE experts participated in four rounds. Rounds 1 and 2 used five web-based questionnaires, including branching-logic software for directed questions to individual panelists. In round 3 (videoconference), the panel finalized the recommendations by vote. During the journal peer-review process, Round 4 was conducted as Web-based questionnaires. Following each round, the agreement threshold for each item was determined as >= 80% for item inclusion and <= 30% for item exclusion. RESULTS: Following rounds 1 and 2, agreement was reached on 62 of 114 items. To the 49 unresolved items, 12 additional items were added in round 3, with 56 reaching agreement and five items remaining unresolved. There was agreement that longitudinal BCCE training must include introductory training, mentored formative training, summative assessment for competence, and final cognitive assessment. Items requiring multiple rounds included two-dimensional views, Doppler, cardiac output, M-mode measurement, minimum scan numbers, and pass-grade criteria. Regarding objective criteria for image-acquisition and image-interpretation quality, the panel agreed on maintaining the same criteria for formative and summative assessment, to categorize BCCE findings as major vs minor and a standardized approach to errors, criteria for readiness for summative assessment, and supervisory options. INTERPRETATION: In conclusion, this expert consensus statement presents comprehensive evidence-based recommendations on longitudinal BCCE training. However, these recommendations require prospective validation.