The determination of the metrics to evaluate the figure of medical science liaison (MSL) presents certain difficulties, as there is a great deal of variability. Therefore, the aim of the present exploratory study is to evaluate the metrics for evaluating MSL performance that are currently being used by the medical departments of the pharmaceutical industry in Spain by using the Delphi methodology with two rounds of participation. After the first round, experts reached a consensus in 20 (38.5%) of 52 items: 18 in agreement and 2 in disagreement. In the second round, they established consensus in 8 (25.0%) of the remaining items. Overall, consensus was met in 28/52 (53.8%) items: 23 in agreement (44.2%) and 5 in disagreement (9.6%). No consensus was reached in 24 items (46.2%). On the general metrics, there was consensus agreement that the weight of each of these metrics should vary according to the product life cycle (96%), and disagreement that performance assessment should be done through a combination of quantitative (92%) and qualitative (80%) metrics. This study provides the company with greater knowledge to establish and adapt its strategies without losing focus on delivering value in the relationships with healthcare professionals and patients.