After 20 years of development, the concept of behavioural additionality (Buisseret, Cameron and Georghiou, 1995) has achieved important conceptual progress. However, when facing the task of identifying and evaluating the behavioural additionality effect produced by innovation and collaboration policies, three important issues remain: conceptual disagreement, the 'black-box' and project fallacy problems, and the need to select a unit of analysis compatible with a holistic perspective on innovation and which does not constrain the type of effects to pre-conditioned behaviours.Motivated by these challenges, this thesis proposes an alternative methodology for evaluating the behavioural additionality dimension of a government-supported policy instrument designed to stimulate and promote collaboration between firms and universities. Thus, in an attempt to close the gap, the thesis explores and merges two complementary frameworks or perspectives: the Case-Based Method (CBM) and the Theory-Based Evaluation (TBE) approach in addition to prior evidence within the evaluation practice of the behavioural additionality effect.The combination of these frameworks results in the proposed methodology, an iterative, three-step evaluation model, where CBM finds its utility as the tool to scope and select the programme focus of analysis, providing an in-depth exploration of the behavioural characteristics of the policy beneficiaries, and TBE helps to develop a programme theory which helps to map the logic of the intervention. In addition to the use of these approaches, another novelty of the approach lies in its incorporation of organisational routines as the unit of analysis (Gök, 2010) and contribution analysis (Mayne, 2012) to attribute policy effects.The methodology is then tested and validated by applying it to six companies (cases) who participated in the Knowledge Transfer Partnerships (KTP) Scheme, a government-supported policy instrument designed to stimulate and promote collaboration by pairing companies with Higher Education Institutions, which has an extensive track record in the UK. The programme was selected due to its potential for stimulating changes in behaviour. The findings of the case studies provide evidence of modifications in behaviours, either by changing the decision-making process that governs the innovation strategy, or by managing to develop new technological components.This research demonstrates the way in which the CBM and the TBE approaches can each be used as a potential research design for evaluating the behavioural additionality effect. Merging these perspectives produces a systematic approach for understanding organisational behavioural change, leading to an improved decision-making process in designing innovation and collaboration instruments that enact the desired influence upon organisational behaviours.