Background: Training has been found effective in improving healthcare professionals’ knowledge, confidence, and skills in conducting advance care planning (ACP). However, its association with their attitudes toward ACP, which is crucial to its implementation, remained unclear. To fill this gap, this paper examines the association between their attitudes toward ACP and relevant training experiences.Methods: An online survey about attitudes toward ACP of healthcare professionals, including physicians, nurses, social workers, and allied healthcare professionals, currently working in hospital and community care in Hong Kong was conducted.Results: Of 250 respondents, approximately half (51.6%) had received ACP-related training. Those with relevant training reported significantly more positive in the perceived clinical relevance, willingness, and confidence in conducting ACP and levels of agreement with 19 out of the 25 statements in a questionnaire about attitudes toward ACP than those without (ps ≤ 0.001–0.05). Respondents who received training only in a didactic format reported a significantly lower level of confidence in conducting ACP than did others who received a blended mode of learning (p = 0.012). Notwithstanding significant differences between respondents with and without relevant training, respondents generally acknowledged their roles in initiating conversations and appreciated ACP in preventing decisional conflict in surrogate decision-making regardless of their training experience.Conclusions: This paper revealed the association between training and positive attitudes toward ACP among healthcare professionals. The findings showed that training is a predictor of their preparedness for ACP in terms of perceived relevancy, willingness, and confidence. Those who had received training were less likely to consider commonly reported barriers such as time constraints, cultural taboos, and avoidance among patients and family members as hindrances to ACP implementation.