The Master's thesis" Planned Continuity: Design of Sustainable Clothing Service Concept" is an experimental design case that proposes service-led approach towards sustainable fashion and clothing. The main objective is to design a service-based clothing concept that would help to maintain satisfying person-product relationships and consequently extend garment life cycles. The thesis can be classified as production-based thesis and it is divided in two equally important parts: theoretical portion and concept development process. The research methods cover literature review and focus group interviews. The theoretical portion focuses on describing sustainable design strategies that have been suggested in favour of product longevity and sustainable consumption. The strategies include product-service systems (PSS), emotional durability, transformability, modular design and participatory design. The concept development rests upon the theoretical findings on the above-mentioned design strategies and focus group interviews. Different steps of the concept development process are described before the final clothing service concept. Furthermore, four modular garments are designed and produced to illustrate how the new concept could actually work in practice. The final clothing service concept embodies a creative design solution where garment life cycle is planned in advance with in-built continuity. The concept includes of a small set of customizable modular garments that in tandem with reassembly service enable more meaningful person-product relationships. Consumer feedback gathered through one focus group interview suggests that the combination of modular garment structure and additional reassembly service may considerably lengthen garment life cycle while still providing satisfaction of a newly bought garment. The thesis questions the traditional way how garments are designed, produced and consumed. What is finally proposed is an alternative design practice that may fulfil consumer needs more responsibly compared to the practices in the current fashion system.