Psychological therapies have been developed for parents of children and adolescents with a chronic illness. Such therapies include parent only or parent and child/adolescent, and are designed to treat parent behaviour, parent mental health, child behaviour/disability, child mental health, child symptoms and/or family functioning. No comprehensive, meta-analytic reviews have been published in this area. To evaluate the effectiveness of psychological therapies that include coping strategies for parents of children/adolescents with chronic illnesses (painful conditions, cancer, diabetes mellitus, asthma, traumatic brain injury, inflammatory bowel diseases, skin diseases or gynaecological disorders). The therapy will aim to improve parent behaviour, parent mental health, child behaviour/disability, child mental health, child symptoms and family functioning. We searched CENTRAL, MEDLINE, EMBASE and PsycINFO for randomised controlled trials (RCTs) of psychological interventions that included parents of children and adolescents with a chronic illness. The initial search was from inception of these databases to June 2011 and we conducted a follow-up search from June 2011 to March 2012. We identified additional studies from the reference list of retrieved papers and from discussion with investigators. Included studies were RCTs of psychological interventions that delivered treatment to parents of children and adolescents (under 19 years of age) with a chronic illness compared to active control, wait list control or treatment as usual. We excluded studies if the parent component was a coaching intervention, the aim of the intervention was health prevention/promotion, the comparator was a pharmacological treatment, the child/adolescent had an illness not listed above or the study included children with more than one type of chronic illness. Further to this, we excluded studies when the sample size of either comparator group was fewer than 10 at post-treatment. We included 35 RCTs involving a total of 2723 primary trial participants. Two review authors extracted data from 26 studies. We analysed data using two categories. First, we analysed data by each medical condition across all treatment classes at two time points (immediately post-treatment and the first available follow-up). Second, we analysed data by each treatment class (cognitive behavioural therapy (CBT), family therapy (FT), problem solving therapy (PST) and multisystemic therapy (MST)) across all medical conditions at two time points (immediately post-treatment and the first available follow-up). We assessed treatment effectiveness on six possible outcomes: parent behaviour, parent mental health, child behaviour/disability, child mental health, child symptoms and family functioning. Across all treatment types, psychological therapies that included parents significantly improved child symptoms for painful conditions immediately post-treatment. Across all medical conditions, cognitive behavioural therapy (CBT) significantly improved child symptoms and problem solving therapy significantly improved parent behaviour and parent mental health immediately post-treatment. There were no other effects at post-treatment or follow-up. The risk of bias of included studies is described. There is no evidence on the effectiveness of psychological therapies that include parents in most outcome domains of functioning, for a large number of common chronic illnesses in children. There is good evidence for the effectiveness of including parents in psychological therapies that reduce pain in children with painful conditions. There is also good evidence for the effectiveness of CBT that includes parents for improving the primary symptom complaints when available data were included from chronic illness conditions. Finally, there is good evidence for the effectiveness of problem solving therapy delivered to parents on improving parent problem solving skills and parent mental health. All effects are immediately post-treatment. There are no significant findings for any treatment effects in any condition at follow-up.