This study done in May 2015 aimed to determine the stages of concern about the K to 12 curriculum which would be adopted at the Grade 11 starting in schoolyear 2016-2017. The researchers were among the participants of the Mandaluyong Upskilling Program (MUP), a special training program organized and implemented by Jose Rizal University for public school high school teachers of Mandaluyong who were expected to be the teachers of the Grade 11 and 12 program. The participants of the study were the researchers’ co-participants at the MUP, representing the four strands of Grade 11-12. Specifically, the study sought to answer the following questions: (1) What concern profile with regard to the implementation of the K to 12 Curriculum will represent the participants belonging to each of the four strands: ABM, STEM, GAS, and HUMSS?; (2) What concern profile with regard to the implementation of the K to 12 Curriculum is prevalent among the MUP participants?; and (3) What are the MUP participants’ predominant stages of concern with regard to the implementation of the K to 12 Curriculum? Seventy teachers were given a 35-item Stages of Concern Questionnaire (SoCQ). Results revealed that in general, the participants consider understanding fully what K to 12 Curriculum, and by extension, the Senior High School levels, entails. While there is a certain extent of awareness as regards the curriculum that can be surmised, teachers still feel that a clearer picture is desired. Comparatively low ratings for impact-related concerns uncover a potential shift in the stages of concern among the participants as the use of the K to 12 Curriculum progresses. In this regard, interventions that may include support programs to address these concerns have been suggested. It has also been noted that the predominant stages of concern among the MUP participants obtained by getting the frequency distribution of highest peaks are Awareness, Personal, and Informational. This again emphasizes that the participants still need to understand what the K to 12 Curriculum means, and what it means for them as teachers.