The purpose of the correlational study was to determine factors that served as barriers to integrative science, technology, engineering and mathematics (iSTEM) implementation in K-12 schools. The sample studied (N = 153) was drawn from classroom teachers and administrators with training in iSTEM methodology or experience in iSTEM methods and subsequent experience regarding implementation barriers. The researcher developed the Integrative STEM Implementation Barriers Instrument (iSTEMIBI). The iSTEMIBI included a six-point Likert scale measuring levels of agreement to statements regarding implementation barriers. The research utilized the Embedded Design correlational model as detailed by Creswell and Plano Clark (2007). Likert items were developed from identified barriers in the literature and from unpublished research by the researcher regarding barriers identified by K-12 teachers completing iSTEM workshops. The research design allowed open-ended response from participants to support the predominately quantitative data. Qualitative analysis of the literature review indicated issues and benefits common to the current iSTEM movement and earlier curricular movements. ANOVA and post hoc Tukey analysis methods were utilized to determine paired differences between groups by Implementation Level, Content Area, and Grade Level within 12 researcher-developed barriers constructs and identified factors (p < .05). Eleven factors impacting implementation were identified through principal component analysis and a subsequent path model was developed.