Attention-deficit/hyperactivity disorder (ADHD) is the most common neurobehavioral disorder of childhood. There is an increasing need to find objective measures and markers of the disorder in order to assess the efficacy of the therapy and to improve follow-up strategies. Actigraphy is an objective method for recording motor activity and sleep parameters using small, computerized, watch-like devices worn on the body, and it has been used in many clinical trials to assess methylphenidate efficacy and adverse effects in ADHD. Our article aim is to systematically review and perform a meta-analysis of the current evidence on the role of actigraphy in both the detection of changes in activity and in sleep patterns in randomized clinical trials that compared methylphenidate against placebo in the treatment of ADHD. A comprehensive literature search of PubMed/MEDLINE, Scopus, Embase, Cochrane Library, CINHAL and PsycINFO databases was carried out to find randomized clinical trials comparing methylphenidate versus placebo in children with ADHD, using actigraphic measures as an outcome. No start date limit was used and the search was updated until June 2013. The primary outcome measures were 'total sleep time' and daytime 'activity mean'. As secondary outcomes, we analyzed 'sleep onset latency', 'sleep efficiency' and 'wake after sleep onset'. Eight articles comprising 393 patients were included in the analysis. Children with ADHD using MPH compared to placebo have a significant difference of a large effect with a diminishing value in the activity mean. For the total sleep time, we found a significant and large effect in the decrease in sleep in MPH group. This study shows that MPH may effectively reduce mean activity in ADHD children, but it may negatively affect total sleep time.