Parent and offspring behaviours are expected to act as both the agents and targets of selection. This may generate parent-offspring coadaptation in which parent and offspring behaviours become genetically correlated in a way that increases inclusive fitness. Cross-fostering has been used to study parent-offspring coadaptation, with the prediction that offspring raised by non-relatives, or parents raising non-relatives, should suffer fitness costs. Using long-term data from more than 400 partially crossed broods of blue tits (Cyanistes caeruleus) we show there is no difference in mass or survival between crossed and non-crossed chicks. However, previous studies for which the evidence for parent-offspring coadaptation is strongest compare chicks from fully crossed broods with those from non-crossed broods. When parent-offspring coadaptation acts at the level of the brood then partial cross-fostering experiments are not expected to show evidence of coadaptation. To test this, we performed an additional cross-fostering experiment (163 broods) in which clutches were either fully crossed, non-crossed, or partiallycrossed. In agreement with the long-term data, there was no evidence for parent-offspring coadaptationon offspring fitness depsite high power. In addition there was no evidence of effects on parental fitness, nor evidnce of sibling coadaptation, although the power of these tests was more modest.