The positive relation between the performance of the client-contractor team and the end-result of a project has led to a growing attention for the human factor in construction procurement exercises. Over the last decade, assessments of constructors’ collaborative behaviour have been used more widely as a partner selection method. One of the most intensive forms of evaluation on soft parameters can be performed via an assessment (centre), also called workshops, with the tenderer’s and client’s team. The purpose of this explorative study is to provide more insights by 1) collecting the client’s motives to use these collaborative tender criteria, 2) identifying the different formats of assessments, and 3) learning lessons from projects that have conducted behavioural assessments. Ten cases are selected across the Netherlands, the United Kingdom and Finland, all of which focus on the procurement phase of a medium to a large-scale infrastructure project. Eleven semi-structured interviews with project and contract managers are used together with five assessor-interviews to gather empirical information. These independent assessors are involved by a public client to score the tenderer’s team during the assessment on a predefined list of sub-criteria. The thematic analysis shows that the use of collaborative criteria can be linked to the development of relational contracting and early contractor involvement. Especially in alliance and design team models with an integrated project team, a high weight is assigned to collaboration in the tender evaluation. Clients also aim to stimulate bidders to be more aware of collaboration and soft skills. The team assessment is applied for this purpose: it assesses the authentic behaviour of key figures that will be working on the project instead of only focussing on written bids. Results reveals that the assessment puts ‘collaboration’ high on the agenda of all parties right from the start, brings the team-related points for attention upfront, and stimulates bidders to approach team composition in another way. Nevertheless, several other instruments could lead to (some of ) the same goals and ongoing attention is needed to utilise the benefits of the assessment. Hence, the attitude and reflection of the client’s team is considered to be crucial for proper implementation. This study shows that the team assessment has proven to enable clients to make a more informed choice for a contractor on its collaborative behaviour. In this way, team assessments can fulfil the potential of being one of the instruments to facilitate high performing teams and project success.