This study drew upon the knowledge base of APA-member practitioners to develop a taxonomy of helpful and harmful practices for treatment with boys and men. Four-hundred seventy five APA-member practitioners solicited from practice-related divisions provided responses to four open-ended questions about helpful and harmful practices in working with boys and men. Qualitative analyses revealed 10 themes that emerged from the analyses. Beneficial and sensitive practices included addressing gender socialization and gender sensitive issues as they apply to boys and men in psychological practice. Harmful practices included biased practices, stereotypes, and a lack of awareness and training around gender and diversity issues as they apply to boys and men. We discuss the specific themes that emerged from analysis of the responses, how these findings are situated within previous work examining helpful and harmful practices, limitations to the study, suggestions for research, and implications for training psychologists.