Purpose: Brand and line extension represents an essential vehicle for growth and is currently one of the most applied marketing strategies within the luxury sector. Though it has its advantages, there are several risks associated with pursuing such a strategy. Consequently, this paper attempts to understand the reasons for brand and line extensions as a way of growth in the new era of luxury expansion. Theory: The study extends the literature of brand and line extensions through an empirical study. Methodology: An integrative model of key success factors behind brand and line extensions is proposed by combining current research with empirical findings obtained through an explorative and qualitative research design based on primary data from eight semi-structured interviews with managers from luxury brands. Findings and Contribution: We identify five key success factors: (1) add value through originality, (2) stay at the level of the brand regarding price, quality, style and image, (3) create relevance to core business and be aligned with DNA, (4) stick to the vision of the founder and (5) assure consistency in brand identity and image. Sig-nificantly, the predominant themes are alignment between the parent brand and the extension and the extension in itself, which resonates with the existing research on the field. Further, drawing on the notion of alignment, this thesis also finds evidence of the importance of consistent brand cues such as storytelling, values, heritage, tradition and visual icons. Practical implications: It is suggested that the five success factors identified in the empirical data to the greatest extent possible should apply to any future brand extension and that resources should be allocated to reinforce the alignment between extension and parent brand. Research limitations: It would be insightful to conduct additional interviews with top managers from other brands to further elaborate on the identified success factors.