Most counselors lack training in play therapy through university counselor education programs, which leaves novice counselors searching for workshops, institutes, conferences, or self-training to effectively meet the mental health needs of children. In this first-of-its-kind study, the researcher investigated relationships between professional development and attitudes, knowledge, and skills in play therapy among working elementary school counselors and professional counselors who are licensed. Professional development consisted of various types of training and/or APT membership. A nonrandom sample of counselors was recruited from relevant online sources in this quantitative study. Attitudes, knowledge, and skills were measured by the self-reported Revised Play Therapy Attitude–Knowledge–Skills Survey (Kao, 2009). Three hypotheses were confirmed at a statistically significant level: Counselors with university-level training had higher levels of attitudes, knowledge, and skills; knowledge in play therapy predicted the skill levels of the counselors; and APT membership related to higher levels of knowledge and skills in play therapy.