In this study, an agile and collaborative systems engineering approach is developed with specific focus on system of systems challenges. First, agility related problems are identified by an interview-based exploratory survey. Afterwards the novel approach is formulated to address agility problems in system of systems environments. The approach is based on eliciting existing knowledge, visualizing it by immediate modeling, verifying consistency of the knowledge by continuous review, and identifying and planning for missing knowledge. Agility is mainly targeted with 1) performing these activities concurrently in modeling workshops, where operational, functional and physical aspects of the solution are developed simultaneously; and 2) with the collaboration of cross domain/organization knowledge sources. Continuous customer training is another tool adopted for enhancing collaboration effectiveness with the customer. The proposed approach was implemented and assessed in a case study in which its potential to increase agility of the systems engineering process in system of systems projects was validated.