In recent Ukrainian state documents on general secondary school educational policy, there was stated the shift from traditional learning technologies to developmental, pupil-centered educational technologies that raise the responsibility of pupils for their learning outcomes. Thus, in the draft state standard of primary general education (2017), project-based learning (PBL) is determined as one of the key educational strategies which build pupils’ cross-cutting skills. PBL involves the use of creative, problem-based, research, group, interactive, presentational, reflective, and other teaching methods, and hence, can provide the formation and development of pupils’ 21st century skills. Unfortunately, the practical experience of PBL in Ukrainian general secondary and higher education institutions today demonstrates limitations of the traditional grading system of pupils’ and students’ performance. In view of this, there is a high necessity to create and implement a new assessment framework that would allow pupils to become really active participants not only in the process of foreign language PBL, but also in evaluating their performance outcomes. It should be a system of assessment that would really involve pupils in evaluation activities, form their self and peer assessment skills. Teachers, in their turn, should pay more attention, first of all, to the process of forming learners’ foreign language personalities which cannot be merely graded. Thе aim of this article is to substantiate the methodological relevance of PBL to the present requirements of the Ukrainian educational system to implement a pupil-centered education at secondary schools. Also, another purpose of this work is to give an overall description of summative assessment of pupils’ performance outcomes of their foreign language PBL. To achieve the purposes stated, there were used such theoretical research methods as scrutiny, analysis, selection, comparison of certain aspects, features, characteristics, and phenomena of the issue under consideration, induction and deduction, generalization, systematization, etc. Thus, the issue of summative assessment of pupils’ foreign language PBL outcomes was considered in this article. The functions, forms, subjects, objects, criteria, instruments, and tools of summative assessment of pupils’ performance outcomes of their foreign language PBL were outlined. Several examples of the assessment instruments to evaluate different PBL assessment objects were given. The prospects of further research studies are concerned with implementing foreign language PBL in Ukrainian general education secondary schools, publishing foreign language PBL course books for pupils, and creating an appropriate PBL performance assessment framework. In this regard, mastering foreign language PBL by Ukrainian teachers and methodological training of tertiary students majoring in foreign language teaching to apply PBL at general education secondary schools, seem to be the mounting questions nowadays.