Integrated STEM labs and makerspaces have become increasingly common in P-16 schools, higher education residence halls, libraries, and community centers. Although these collaborative learning spaces provide increased access to cross-cutting science, technology, engineering, and mathematics (STEM) practices, they pose inherent safety risks that are often overlooked. This study utilized a concurrent quasi-mixed design (Teddlie & Tashakkori, 2006), to investigate changes in the safety perceptions of educators' from 21 school districts. Pre- and post-survey ratings were mixed with content analyses from open-ended survey questions and accident report forms. The findings suggested that the PD experience had a significant influence on participants' safety perceptions; however, there were no significant differences according to certification areas. The analyses also revealed female participants' reported significantly greater safety self-efficacy gains than males. Additionally, 82% of the sample indicated the PD positively influenced their makerspace and integrated STEM safety knowledge. The findings indicate that high-quality safety PD can significantly influence educators' perceptions (especially females) about safer integrated STEM teaching and learning in makerspaces. This study provides implications for STEM educators, librarians, administrators, teacher educators, researchers, state education departments, school district safety officers, and others to improve the safety of cross-cutting STEM learning occurring in collaborative environments.