Purpose: The purpose of this study is to find out what activities of ambidexterity impact start-up companies’ efficiency and business growth in Sweden’s market.Methodology: To understand the research objectives, a qualitative study with 10 in-depth and semi-structured interviews was conducted with startup companies, founders and managers to gain insights.Findings: This study identified two new constructs; environmental dynamism and company nature, that are novel to measure ambidexterity start-up business performance.Research limitations/implications: The focus on Swedish startups limits the transferability. Therefore, future research should be conducted in other countries or in different context settings.Originality/value: This study contributes to the entrepreneurial research proposing proactive and reactive engagement with clients and contributes to strategic leadership theory, identifying that organization such as self-learning and collaboration fosters innovation among employees