Chronic pain and insomnia are highly comorbid: Approximately 50% of those with chronic pain experience insomnia or clinically significant sleep disturbances, and 50% of those with insomnia experience chronic pain. Further, these conditions can be extremely disabling, particularly when they co-occur. There is increasing recognition of the need to tackle both chronic pain and insomnia together, as evidenced by growing empirical research in this area. Cognitive processing biases have been independently implicated in both chronic pain and in insomnia. Given their trans-diagnostic status, cognitive biases may therefore have a role in explaining the co-occurrence and mutual maintenance of these conditions. These biases also represent novel, potentially modifiable targets for treatment. However, the role of cognitive biases has not been adequately explored in comorbid chronic pain and insomnia. Here, we describe the state of cognitive bias research in chronic pain and insomnia, considering evidence for the roles of attentional bias, interpretation bias, expectancy bias, and memory bias. In reviewing the literature, it is apparent that similar cognitive biases operate in insomnia and chronic pain, with preliminary, albeit sparse, evidence of pain-related cognitive biases influencing sleep-related outcomes. On the basis of current findings and separate theoretical models, we present a novel, testable cognitive model of comorbid chronic pain and insomnia, to guide future research in this area. Key recommendations for the future of this relatively new field are provided. Perspective: Chronic pain and insomnia are highly co-morbid, suggesting an overlap in causal mechanisms. Empirical research, although sparse, suggests that cognitive biases may play a role in their development and mutual maintenance. Our novel cognitive model generates research avenues of clinical importance for treating co-morbid chronic pain and insomnia.