Effective cross-functional relationships (CFRs) are a key success factor in developing successful new products for many companies. This paper adds to our existing knowledge on the Marketing/R&D CFR by examining the effects of communication behaviours, micropolitics and interpersonal trust on the dependent variable, interpersonal collaborative behaviour during NPD activities. Interpersonal collaboration is seen as a higher level of working relationship which incorporates a "volitional" and "trusting" aspect to working relationships. Our findings reveal that the perception of the Marketing Manager as a political ally has a positive effects on interpersonal collaborative behaviour. Further, affect-based trust has a strong effect on collaborative behaviours indicating that a benevolence aspect of working relationships is critical for collaborative behaviours to emerge during NPD.