Purpose: This study aims to explore the differences between large companies and family SMEs in the development of sustainable and innovative products, focusing on critical success factors specific to each type of company.

Design/methodology/approach: The analysis is based on a multiple case study, examining two Italian companies in the textile sector. Semistructured interviews were conducted with managers and members of product development teams, supplemented by secondary data. The analysis was carried out through thematic coding and cross-case comparison, with the aim of identifying recurring patterns and size-related differences. A benchmarking approach was used to highlight similarities and divergences in sustainable product development processes.

Findings: The findings reveal that ownership plays a crucial role in family-owned SMEs, significantly impacting ideation, strategic partnerships and sustainable product development processes. Ownership not only facilitates constant idea exchange but also drives strategic connections and collaborations essential for innovation. The study, using Brown and Eisenhardt’s framework, highlights how ownership influences team dynamics, work organization and supplier integration, which are pivotal for NPD. Unlike large firms, family-owned SMEs lack formalized cross-functional teams, relying on senior management for external communication and maintaining agility through an iterative approach. This structure enhances adaptability, supporting rapid product innovation aligned with the company’s sustainable mission.

Originality/value: This study offers an exploratory and context-specific contribution by examining how family ownership influences sustainable product development (SPD) and how firm size shapes the expression of critical success factors (CSFs). Rather than claiming statistical generalizability, the study generates in-depth insights into the mechanisms – such as ownership-driven ideation, informal coordination and supplier integration, that explain how and why size and ownership matter. By focusing on Italian family firms, the research also highlights the role of culturally embedded traits such as practical problem-solving, resourcefulness and artisanal creativity, extending international NPD frameworks to a specific national setting.