As influencer marketing continues to grow as a central component of many companies' marketing strategy, the ability to accurately measure campaign effectiveness has become increasingly important. While substantial financial investments are allocated to influencer campaigns, current measurement practices vary considerably in their ability to capture actual business performance. This study examines how companies measure the effectiveness of influencer marketing campaigns and how these practices are shaped by campaign objectives and internal capabilities. Using a qualitative approach, nine semi-structured interviews were conducted with marketing managers at Swedish companies and influencer marketing agencies. The findings indicate that indirect metrics, particularly engagement, dominate current measurement practices. This reliance is primarily driven by long-term brand awareness objectives rather than driving short-term sales. Direct measurement of purchase behavior remains limited and is largely dependent on companies' distribution models and internal analytical capabilities. Attribution emerges as the most significant challenge as the non-linear nature of the customer journey and concurrent marketing activities make it difficult to isolate the contribution of specific influencer campaigns. Beyond this, access to measurement tools was found to be particularly important in determining a company's ability to track direct outcomes such as conversion and sales. By applying the Hierarchy of Effects model and the Resource-Based view, this study demonstrates that measurement practices are shaped by both campaign objectives and internal resource constraints.